'&) CJeWey HD28 .M41A iHI MIT LIBRARIES 3 9080 00932 7856 Econometric Evaluation of Asset Pricing Models August 1993 Revised July 1994 WP Sloan 3606 Lars Peter Hansen University of Chicago, NBER and NORC John Heaton and NBER M.I.T. , Erzo Luttmer Northwestern University Correspondence and requests for reprints to: John Heaton Sloan School of Management E52-435, MIT 50 Memorial Drive Cambridge, MA 02142 (617) 253-7218 We thank Craig Burns ide, Bo Honore, Andrew Lo, Marc Roston, Whitney Newey, Jose Scheinkman, Jean-Luc Vila, Jiang Wang, Amir Yaron and especially Ravi Jagannathan, Richard Green (the editor) and an anonymous referee for helpful comments and discussions. We also received valuable remarks from seminar participants at the 1992 meetings of the Society of Economic Dynamics and Control, the 1992 NBER Summer Institute and at Cornell, Duke, L.S.E. and Waterloo Universities. Finally, we gratefully acknowledge the financial assistance of the International Financial Services Research Center at M.I.T. (Heaton), the National Science Foundation (Hansen and Heaton) and the Sloan Foundation (Heaton and Luttmer). Abstract In this paper we provide econometric tools for evaluation the of intertemporal asset pricing models using specification-error and volatility bounds. We formulate analog estimators of these bounds, give conditions for consistency and derive the limiting distribution of these estimators. analysis incorporates market frictions such as proportional transactions costs. use the methods to assess The short-sale constraints and Among several applications we show how to specific asset pricing models and nonparametric characterizations of asset pricing anomalies. JUU281995 LlBRAR,ES to provide In this paper we provide statistical methods for assessing asset-pricing using models procedures specification-error can account for volatility and market frictions short-sale constraints, and are easier to interpret For these implement, the most part transactions to asset-pricing models. statistical The bounds. due costs or tests of than standard methods are quite easy to They are designed to even when market frictions are considered. failures of some popular provide a better understanding of the statistical asset-pricing models and to offer guidance in improving these models. Models of asset pricing with frictionless markets imply that asset prices represented by a stochastic discount factor or pricing kernel. can be stochastic discount and, For example, "discounts" payoffs in in the Capital Asset Pricing Model given by a constant plus a scale multiple of portfolio. each state of world the adjusts the price according to the riskiness of the as a consequence, payoff. is factor A the discount factor return on the market the In the Consumption-Based CAPM the discount factor is given by the intertemporal marginal rate of substitution of an investor. The implications of particular models with observable (up to a finite number of parameters) stochastic discount factors are often tested by looking directly at the average "pricing errors" of the models. Formal statistical tests are performed using a time series of portfolio payoffs and prices by examining whether the sample analogs of the average and predicted prices are significantly procedure, different see Hansen from and each other. Singleton examples For (1982), Brown this of and Gibbons type of (1985), MacKinlay and Richardson (1991) and Epstein and Zin (1991). While tests such as these can be informative, interpret the resulting statistical rejections. directly applicable costs or short-sale when there constraints. are market Extending it is often difficult Further, frictions the such models to these tests are not to as transactions allow for such frictions entails inequalities instead of the pricing equalities that prevail in frictionless market models 1993). can not tests these Finally, see Prisman (e.g., 1986 and Jouini and Kallal used when be candidate discount the factor depends on variables unavailable to the econometrician. As an alternative to considering the average pricing errors of a model, consider we different a specification-error bounds volatility set bounds of Hansen tests of Hansen of Jagannathan Jagannathan and diagnostics and and using the and the (1993), We (1991). also consider extensions of these tests and diagnostics, developed by He and Modest (1993) and Luttmer (1994), that handle transactions costs, short-sale restrictions We develop an econometric methodology to provide and other market frictions. consistent estimators of the specification-error and volatility bounds, and an asymptotic distribution theory that is easy to implement and that can be used to make statistical inferences. Among other whether a volatility information specific model bounds results the things, the of implicit about the in means in this paper allow one stochastic returns; deviations standard and factor discount asset-market to: test satisfies the compare the (ii) of (i) discount factors contained in different sets of asset returns; and (iii) test hypotheses about the size of possible pricing errors of misspecified asset pricing models. While Burnside and Cecchetti, (1994) Lam and Mark tests of models of the discount factor along the lines of are based on a parameterization different yields accommodate market (ii), our results parameterization tests frictions permit in these that a are of the simpler to among data (iii) is to shift the focus of statistical analyses Our bound. and implement In sets independent of a specific stochastic discount factor model. for their tests (i), volatility straightforward manner. comparisons have devised (1993) can regards to be to made Our motivation of asset pricing away models whether from the models correctly are specified and towards measuring the extent to which they are misspecif ied. The rest of the paper is organized as follows. the 1993), volatility and specification He and Modest (1993) bounds and Luttmer In Section Hansen of (1994). we review 1 Jagannathan and (1991, We show formally that the volatility bound can be viewed as a special case of the specification-error bound. This permits us develop the underlying econometric to tools in a unified way. In Section 2 we provide consistency and asymptotic distribution results estimators for applications our of results Section independently. the of 3. of bounds. In Section 2, A shows how to use models of the discount factor. In Section each of present we 3 which be can the volatility bounds Section 3.B we extend to two read test distribution the theory of specification-error bound to the case where there are parameters of the discount factor proxy that are unknown and must be estimated. Section discusses 4 the distribution limiting parameters the of underlying the bounds both with and without market frictions. things, is these results can be used to determine whether the volatility bound degenerate sharpens Among other the or more bound. generally whether Finally, Section additional 5 describes security some market extensions data and provides some concluding remarks. 1. General Hodel and Bounds Our starting point is a model in which asset prices are represented by a stochastic discount factor or pricing kernel. pricing subject to transactions costs, we constraints for a subset of the securities. is an extreme version of a transactions cost, To accommodate security market permit there to be short-sale Although a short-sale constraint other proportional transactions . costs such as bid-ask spreads can also be handled with this formalism. in Foley is done as constructing according A short-sale constraint sold. and Kallal Jouini (1970), payoffs two to whether (1993 ^ and Luttmer security a is (1994) by purchased or securities to imposed on both artificial is This and a bid-ask spread is enforce the distinction between a buy and a sell, modeled by making the purchase price higher than the sale price. Suppose vector of security market payoffs used the analysis is denoted The vector x x. is used to in an econometric generate a collection of payoffs formed using portfolio weights in a closed convex cone C of R P = {p : to C [x ' R is ,x '] where constraints constraints. More . and the contains x If partition generally, contains x (1) incorporate all of the short-sale constraints imposed in the econometric investigation. then : p = a'x for some a € C} The cone C is constructed n n k the there are no market frictions, x components two not subject components I components: into subject to to x' = short-sale short-sale Then the cone C is formed by taking the Cartesian product of R and the nonnegative orthant of R I . Let q denote the random vector of prices corresponding to the vector x of securities payoffs. assets are traded and These prices are observed by investors at are permitted to be random because reflect conditioning information available to the investors. the the time prices may In the absence of short sales constraints, prices can be represented by: where m q = E(mx|?) is a stochastic (2) discount factor and ? is the information set available to investors at the time of trade. Since it is difficult to model empirically the conditioning information available to investors, we instead work with the average or expected value of (2): Eq Some - Emx = conditioning (3) . information can be incorporated in the usual way by multiplying the original set of payoffs and prices by random variables in the conditioning information of economic agents. More generally in the case of market frictions, x is partitioned in the manner described previously and the pricing is represented by: Eq Eq n - s - = Emx" Emx s £ (4) . For notational simplicity we write (4) as: Eq - Emx € C (5) where the elements of C are of absence of frictions we take C encompasses (3). The vector of payoffs x s the to contain only the zero vector so that (5) pricing the inequality subject to nonnegative. In the form (0,0')', restriction (3 emerges because short-sale constraints must allow for the possibility that these constraints bind and hence contribute positively to the market price vector. Haintained Assumptions l.A There are three restrictions on the vector of payoffs and prices that are central to our analysis. the second The first is a moment restriction, to the absence of arbitrage on the space of portfolio payoffs, is equivalent and the third eliminates redundancy in the securities. For pricing relation (5) to have content, we maintain: Assumption 1.1: Assumption 1.2: Further for a € <«, £|q|< £|x| For any a € C, C, a' Eq £ a.' Eq if a'x £ > Recall that C is the Cartesian product of R I IR , which captures Assumption 1.2 is the a and Probia' x > 0} > 0. if a'x = 0. short-sale statement of expected prices and modified to and the nonnegative orthant of restrictions on some the of the securities. Principle of No-Arbitrage applied account for the fact that C need not to be linear [e.g., see Kreps (1981), Prisman (1986), Jouini and Kallal (1993), and Luttmer (1994)]. It guarantees that there exists a non-negative stochastic discount factor m with finite second moment such that (5) holds. Kallal (1993) discuss additional assumptions that imply Jouini and the existence of a positive discount factor satisfying (5), however in our analysis we consider only nonnegative discount factors. Next we limit the construction of x by ruling out redundancies in the securities: Assumption 1.3: a = a . If a'x = a 'x and a' Eg = a ' Eq for some a and a in C, then In the absence of transaction costs, Assumption 1.3 precludes the possibility that the second moment matrix of x is singular. a nontrivial probability one. linear combination of linear light of In combination would (5), have to Otherwise, there would exist the payoff vector x the (expected) price of be zero, violating that is zero with this nontrivial Assumption To 1.3. accommodate securities whose purchase price differs from the sale price, we permit second moment matrix of the Assumption requires then 1.3 composite vector x to be singular. the distinct that portfolio l.B used weights construct the same payoff must have distinct expected prices. to 2 Minimum-Distance Problems There are two problems that underlie most of our analysis. M denote Let the set of all random variables with finite second moments that satisfy (5), and let M be the set of all nonnegative random variables in M. Assumption implies 1.2 satisfies so (5) that there that is a nonnegative both sets are nonempty. variable for a stochastic discount factor that, satisfy relations (5). Let discount y denote Recall that factor some 2 = "proxy" strictly speaking, does not Following Hansen and Jagannathan (1993), we consider the following two ad hoc least squares measures of misspecif ication: 8 that min £[(y mzM - m) min £[(y meM - m) 3 2 ] , ] . (6) and 2 (7) Clearly, the specification-error bound implied by (7) is no smaller than that implied by (6) since solutions to (6) and it (7) is obtained using a smaller constraint set. The are the objects we are interested in estimating and s inferences making Sections about. and 2 provide 3 large-sample justifications for the solutions to sample counterparts to these optimization problems. setting By collapse the finding to proxy to y bounds on the zero, the second error problems stochastic discount specification moment of factors as constructed by Hansen and Jagannathan (1991), He and Modest (1993) and Luttmer (1994). In particular, derived bounds the in Hansen Jagannathan (1991) are obtained by setting y to zero and solving (6) and when there are no short-sale constraints imposed (when C is set to R n ); and (7) the bound derived in He and Modest (1993) is obtained by solving (6) for y set to and the bound derived by Luttmer (1994) zero; y set to These second zero. deriving feasible regions for means is obtained by solving and (7) subsequently be used bounds will moment for in standard deviations of stochastic and in developing discount factors. In solving the squares problems least (6) and econometric methods associated with those problems, study the conjugate maximization problems. 5 2 2 = max{Ey aeC = max {£y - £[(y - x'a) 2 ] it (7) is most convenient to They are given by - 2a' Eg} (8) , and S 2 where the notation h 2 - £[(y - x'a) +2 denotes max{h,0}. by introducing Lagrange multipliers on ] - 2a' Eg} (9) The conjugate problems are obtained the pricing constraints exploiting the familiar saddle point property of in the Lagrangian. (5) and The a' then have interpretations as the multipliers on the pricing constraints. The conjugate problems in (8) and (9) are convenient because the choice variables are finite-dimensional vectors whereas the choice variables in the original least squares problems (6) and (7) are random variables that reside possibly in problem infinite-dimensional constraint sets. the conjugate problems are justified formally of 1993) and Luttmer (1991, and S estimators of S and so In (9). solutions In is a standard quadratic programming problem. (8) doing problems to in fact, optimization The specifications Hansen and Jagannathan In Section 2 we develop the properties of (1994). based on time series sample analogs to problems (8) rely we and (8) on (9) several important and an on proprieties additional of the identification assumption. Notice that the criteria for the maximization problems are concave in a and that the first-order conditions for the solutions are given by: Eq - - £[(y x'a)x] e C (10) in the case of problem (8) and Eq - + EUy - x'a) x) € in the case of problem (9), Interpreting conditions. C (11) along with the respective complementary slackness the first-order conditions for these problems, observe that associated with a solution to problem (8) is a random variable m = (y - x'oc) in M and associated with nonnegative random variable m = the unique (up to (y - x' a)* a solution in M* . to problem (9) is a These random variables are the usual equivalence class of random variables that are equal with probability one) solutions to the original least squares problems (6) and (7). Consistency of the estimators of 5 and 5 relies upon the fact that the Compactness in the case of (8) sets of solutions to (8) and (9) are compact. is easily established. Since Assumption 1.3 eliminates redundant securities and the random variable - (y x' is uniquely determined, a.) conjugate problem (8) is also unique. criterion must be the same for all however. case this In x' a) is uniquely determined, hand, the random variable (y - x'a) as solutions, implying that they all must The solution to conjugate problem (9) may have the same expected price a' Eg. not be unique, the solution a to This follows because the value of the is the truncated random variable - (y the expected price a' Eg. On the other is not necessarily unique, so we can not exploit Assumption 1.3 to verify that the solution a is unique. The set of solutions is convex due to the concavity of the criterion and the convexity of the constraint set. in asymptotic distribution As is typical need an identification restriction that a sufficient is also compact. it theory, there is a in Section 2 we will unique solution to except when all prices are constant. conjugate problems, solutions is convex, the As is shown in Appendix A, Since the set of local uniqueness implies global uniqueness. condition for local uniqueness, let x the To display denote the component of composite payoff vector x for which the pricing relation is satisfied with equality: = Emx* where g x Eg* (12) is the corresponding price vector. may contain elements of x event {m>0>. s . Let 1,~ „, Notice that in addition to x Ex x 'l/~ >0 \ is nonsingular. 10 , be the indicator function for the A sufficient condition for local uniqueness is that Assumption 1.4: n To why see this complementary is valid a sufficient conditions slackness we condition, know observe that multipliers the a from are the zero whenever the pricing constraints are satisfied with a strict inequality. a result m is given by (y - x E« £ = ^ { '/3) for some vector Eixx,1 S>o} As and consequently, J3, (13) Cm >o}^ When the matrix £(x x 'l/~ sn i) is nonsingular, we can solve (13) for {m>0> l.C Volatility Bounds and Restrictions on Means The second moment bounds described in the previous subsection can be converted into standard deviation bounds via the formulas: a o- ~2 where 6 2 = IS = r - ~2 [8 - {Em) ,„ W2 2 (14) ] ,2,1/2 (Em) ] ~2 and 6 are constructed by setting the proxy to zero. Em is equal to the average price of the unit payoff when trade in this payoff is not subject to transaction costs. there If are transactions costs or if no data is available on the price of a conditionally riskless payoff then Em cannot be identified. In these circumstances, volatility bounds can still be obtained for each choice of Em by adding a unit payoff to P (augmenting x with a and assigning a price of Em to that payoff (augmenting Eq with Em). 1) In forming the augmented cone, there should be no short-sale constraints imposed on the additional obtained using (8), security. (9) Mean-specific volatility bounds can then be and (14). Although Em may not be identified, the Principle of No-Arbitrage does ooo put bounds on the admissible values of Em: Em € [A ,v ] where A is the lower bound arbitrage and v arbitrage upper the is bounds These bound. are computed using formulas familiar from derivative claims pricing: infia'Eq A = - v s infia'Eq a e C and a'x 2 -1} : a € C and a'x 2 1} : is always well defined via While X (15) (15), v (16) may not be because there may not exist a payoff in P that dominates a unit payoff. define v v to be In Section 2 we show how to consistently estimate X +00. Consistent estimation of these bounds is important . deviation bound we and since the standard is infinite for choices of Em outside these bounds. <r Estimation of the Bounds 2. section this In results for the we develop consistency prices are associated (x. ' ,q ' ,y and replicated with the )' } whose over time composite sequence that is some in vector of joint distribution of (x'.q'.y)'. the data on asset (x'.q'.y)' empirical is a (Borel measurable) is distribution in Section stationary payoffs and That fashion. a stochastic distributions A key 1. is, process approximate the We denote integration with respect to the empirical distribution for sample size T as T. that asymptotic specification-error bounds presented presumption underlying our analysis { In such circumstances, function of More precisely, (x' ,q' ,y) with a for any z finite first moment, we will approximate £z by T.z where j;z = H/T)£ =i z t (17) . \?. Among other things, we require approximation becomes arbitrarily this that That is we presume that {z good as the sample size T gets large. Law of Large Numbers. A sufficient condition for this is: Assumption 2.1: composite The process i(x ' ,q ' ,y )} } obeys a stationary and is ergodic. Under this assumption, we can think of (x'.q'.y) as (x 4 ' ,q ' ,y ). To estimate the specification-error bounds, we suppose that a sample of size T is available and that the empirical distribution implied by this data is used the population distribution. in place of [Thus we are applying the Analogy Principle of Goldberger (1968) and Manski (1988)]. random functions 4> We introduce two and #: >(a) = y i(a) = y 2 - (y - a' x) - (y - a'x) 2 - 2a'q, (18) and 2 (d ) T = 2 max +2 - 2a'q y[i(a)] . (19) (20) tt€C and 13 2 (d 2. T [0(a)] max aeC = ) T (21) . Consistent Estimation of the Specification-Error Bounds A establish first We sequences {d and {d > the statistical consistency estimator the of }: almost surely to 5 and <5, respectively. The proof of this proposition is given in Appendix A and is not complicated by the presence population and of short-sale sample constraints. criterion functions basic The for concave and the sets of maximizers are convex. idea conjugate the that the problems are is By Assumptions 1.1 and 2.1, the criterion functions converge pointwise (in a and 6) almost surely to the population criterion functions introduced in Section l.B. concavity of the criterion functions, sets almost surely [for example, see Rockafellar (1970)]. sets maximizers of the of limiting light In the of this convergence is uniform on compact criterion Finally, since the functions are compact, for sufficiently large T one can find a compact set such that the maximizers of the sample and population criteria are contained see Hildenbrand example, (1974) that in compact set [for Hence the conclusion and Haberman (1989)]. follows from the uniform convergence of the criteria on a compact set. 2.B Asymptotic Distribution of the Estimators of the Bounds We consider sequences objects of of the next the limiting specification-error interest as solutions to distribution bounds. the 14 Our conjugate of the analog ability problems to estimator express permits us the to obtain results very similar to those in the literature on using likelihood ratios devices as selection model for in environments models when are possibly misspecified [for example, see Vuong (1989)]. We show that when the specification error bounds are positive, limiting distribution we obtain a that is equivalent to the one obtained by ignoring parameter estimation, when specification the error bound is zero the and distribution limiting is [See Theorem 3.3 of Vuong (1989) page 307 for the corresponding degenerate. result for likelihood ratios.] be a maximizer of T $> Let a T (j>, a and maximizer a of a a maximizer of study To £0. the E<p, limiting a a maximizer of behavior of the estimators, we use the decompositions: \/T[(d 2 ) T 2 - I ) = •T^.[0(a ) - i(a)] + /T^liu) - ) - $(£)] + /T^tfU) - £0(a)] T E*U)] (22) , and 2 •T[(d ) - 5 2 T ] = /I^[$(Z T . (23) We make the following assumptions: Assumption 2.2: *(a) - E*(a) **, converges in distribution to a [{mx - q) - Eimx - q)] normally distributed random vector with mean zero and covariance matrix Assumption a 2. 3: y% ^(a) - £0(a) V. converges in distribution to [(mx - q) - E(mx - q)]_ normally distributed random vector with mean zero and covariance matrix More primitive assumptions that imply the central limit V. approximations underlying Assumptions 2.2 and 2.3 are given by Gordin (1969) and Hall and Heyde (1980). Let denote u followed by selection a + k one a in its first position distributions limiting The zeros. I with vector the for specification-error bound estimators are given by Proposition 2.2: Proposition 2.2: - 2.1 2.3, As Suppose that WT[d 2.2, WT[d - 8]} - other maximizers by negligible. converges indicates values depend only on In 6*0. and to Under Assumptions 1.1 - 1.3, normally distributed random vector a 5]> converges in distribution to a normally distributed random Proposition 2.2 (23). 5*0 the second the words, sample the the limiting distributions terms impact maximizers replacing in the the in unknown criterion sample maximized the decompositions the of of for (22) and population functions is As a consequence the presence of short-sale constraints does not complicate the limiting distribution. To see why the asymptotic distribution in Proposition 2.2 is not affected by sampling error in the estimation of the multipliers, consider the ~ case of the sequence {(d) ~ 2 }. By the concavity of <f>, we have the following gradient inequalities: (24) [(mx - q) - E(mx + However, it follows from E(mx the - q) (a - q)]-(a^ - a) first-order 16 - a) . conditions (including the complementary slackness conditions) for the population conjugate problem that (25) constrained to be in Since, a Combining (24) and (25) we have that £ /TEjtfU^ £ VT^Umx if Limit the - 0(a)] - q) by Assumption 2.3, Central zero C. Theorem, (26) qU-(i E(mx - - the sample counterparts of the pricing errors obey {v'TY [0(a - ) 0(a) maximizers can be chosen so surely to zero. - a) ]> that converges {(a - in a)} probability to converges almost This latter convergence can be demonstrated by exploiting the concavity of the population criterion function and the convexity of the constraint [for set example, see the discussion on page 1635 of Haberman (1989) and Appendix A]. To u'Vu or use Proposition 2.2 Consider u'Fu. sequence {0 (a ): t=l,2,3, the ... practice in case T> of requires u'Vu. For consistent each T estimation of form the scalar and use one of the frequency zero spectral density estimators described by Newey and West (1987) or Andrews (1991), for example. As is shown in Appendix A, when the price vector q is a vector of real numbers (degenerate random variables), the asymptotic distribution for {v^Tld - 6]> remains valid even when the population version of the conjugate maximum problem fails to have a unique solution this case, the lack of identification of (Assumption 1.4 the is violated). parameter vector a does not alter the distribution theory for the specification-error bound. 17 In While this special case is of conditioning using Section interest, considerable information it rules out synthetic form to the payoffs possibility of described as in 1. Notice that if 5 = Proposition 2.2 breaks down. or 8 = 0, This occurs if y is a valid stochastic discount factor in which case the solutions to the population conjugate problems are a = a = 4> are (a) both "2 distribution for Wl(d convergence of the giving zero identically ~ and Wl(d^) 2 As a consequence, 0. rise to a Our results <f> degenerate (a) and limiting in Section 4 on the parameter estimators can be used to establish that the } ) "2 rate of convergence of {(d) ~ > }. and {(d) 2 } and is given by a weighted is T, utions (see Vu converge at the rate v'T, although the limiting distribution is not normal. Consistent Estimation of the Arbitrage Bounds 2.C As we discussed in Section into standard deviation bounds 1, the second moments bounds can be converted the mean of m if estimated using the price of a risk-free asset. be prespecif ied. not is is known or if it can be When Em is not known it must Let v be the hypothesized mean of m when a risk free asset available. Proposition 2.1 can be applied to establish the consistency of the second moment bound estimators for each admissible price assignment v. In the case of 5 , for the price assignment to be admissible, must not induce arbitrage opportunities onto the augmented collection of it asset payoffs and prices. (A ,d o ) o Any price (mean) assignment in the open interval is admissible in this sense, The final question we explore in this section is whether the arbitrage bounds, A and u given in (15) and (16), can be consistently estimated using the sample analogs: -infia'Yq = t a € C and : a'x (27) * -1 for all t-1,2, . . ,T> . and infia'Yq = u : a € C and a'x The estimated upper arbitrage i 1 bound (28) for all t-1,2 u is T> always . when finite there is a payoff on a limited liability security that is never observed to be zero in Our estimated range of the admissible values for the the sample. price of a unit payoff and hence mean of n is [I ,u Notice ]. (average) these that linear programming problems. bounds can be computed by solving simple In Appendix A we prove: almost surely. If v Consistent 2.D is finite, Estimation then {u the of } converges to v Feasible Region of almost surely; and Means and Standard Deviations We now consider consistent estimation of the set of feasible means and standard deviations of that for given a mean stochastic discount of the stochastic factors. discount deviation bound can be consistently estimated. stochastic discount factor typically is not Previously we factor, However, known. As the a the showed standard mean of result it the is important to understand the sense in which the entire feasible region can be approximated. Such a region can be computed with or without no-arbitrage restriction that Let S the stochastic discount imposing the factors be positive. denote the feasible region without positivity and S* the (closure) of Similarly, the feasible region with positivity The question we now turn sample counterparts. and S S* good approximations to S let S fco and the S* denote the is in what sense are S and ? When there is a unit payoff, all four feasible regions are vertical rays in standard deviation space because mean and rays S o and S the more usual . case when data on the price of a unit payoff is not matters are a little more complicated. longer vertical instead are unions but rays represented (possibly as (hypothetical and mean), convergence counterparts. of extended) our the real-valued previous sample The feasible regions are such rays of The boundaries of convex sets with nonempty interiors. mean) this of o available, no price (average) and S* can be estimated consistently by the points of origin of the corresponding rays S In the In this case the points of origin of the payoff is the mean discount factor. analysis analog functions to in these sets can be functions implies resulting of the ordinate pointwise their the (in population This result implies uniform convergence of the sample analog functions in following sense. Since estimated, the lower and upper for large enough T, arbitrage are finite on any compact subset of (A ,v ). functions are finite on any compact subset of convex functions result [see Theorem 10.8 of Rockafellar of converge uniformly, the bounds can be consistently the sample analog functions under positivity hypothetical almost surely, When positivity is ignored the R. mean of (1970)] Further these functions are the discount factor. As the sample analog functions on any compact subset of (A ,v ) in case of positivity and on any compact set when positivity is ignored. difficulty is that the approximations deteriorate as the mean assignment, approaches the arbitrage bounds large when positivity is ignored. in a the case of positivity, the One v, or when v gets . arbitrage bound turns out not be problematic. to To see this, instead of viewing the boundaries of the feasible regions as functions of the ordinate, we explore the approximation error from a set-theoretic vantage point in Consider first the case in which v < (R . Associated with a sample of size T +00. is an approximation error as measured by the Hausdorff metric: max<n(S ,S (29) ,S )> TO ),tt(STO where: n(K ,K 12 Measuring ordered = ) the pairs sup )eK approximation get to measures of distance, as )-lv,w)\ \(v ,w 222 )€K (v ,w via error 1 (30) 1 Hausdorff the restricting without close them metric have to allows same the we no longer confine our attention to "vertical" In other words, ordinate. inf 111 (v ,w the is when we view case the boundaries of the feasible regions as functions of the hypothetical (expected) prices of a unit The added flexibility in the Hausdorff metric permits us to exploit payoff. better consistent the estimation of the upper and arbitrage lower bounds (Proposition 2.3) When v is infinite, the approximation error t> defined by (29) will be As a remedy, we replace n by infinite. (C ,C re P * ) 2 = sup (.. ... inf \~v Osv sp (., ... |(v ,w )-(v ,w \^v 1 1 2 )| 2 (31) where p is any arbitrary positive number greater than Under Assumptions 1.1-1.3 and 2.1, Proposition 2.4. {y arbitrage lower the converges to zero > almost surely. proposition This estimated follows This and the arbitrage the lower bounds can boundaries of consistently be {S approach } the uniformly on any compact interval within the arbitrage lower boundary of S bound. since (Proposition 2.3) latter convergence follows from Proposition and 2.1 the convexity of the boundary. 3. Applications two applications of the analysis of Section In this section we discuss First 2. we show standard-deviations how can be feasible the used to test a regions for specific model of and means the the discount factor. Burnside (1994) and Cecchetti, Lam and Mark (1993) have developed a version of constraints implemented Section there 2. are this test when or transactions in a there are costs. We relatively simple no assets demonstrate manner by subject how to this exploiting the short-sale can be results of test Further we formulate the test so that it is also applicable when assets subject to short-sale constraints. As a result this provides (large-sample) statistical foundation to the tests of asset pricing models suggested by He and Modest (1993), and Luttmer (1994). Second we outline an extension of the specification-error bound analysis that is useful when the discount factor proxy under consideration depends upon a vector of unknown parameters. We consider how these results can be used to select between two nonnested models by comparing the minimized values of the specification-errors. Testing a Specific Hodel 3. A of Factor using Volatility Discount the Bounds Suppose that in addition to asset-market data, a model of the discount factor is posited and a time series of observations of the discount factor is available: whether {m satisfies it One way to test T}. t=l : the model volatility bounds discussed in Sections the a unit payoff can be estimated by the mean of m. the original vector with a payoffs of and 1 Specifically, unit form x by form q by payoff; augmenting the original vector of prices with the random variable and form m; C by constructing the the Cartesian product of the original cone with effect, we have added a subject to results Section of functions short-sale constraint. a and 4> subtracting m 4> 1 2.B and R. In is not can apply the payoff with an average price m that unit forming a In with one minor test, we modification. are now constructed by setting 2. the average price of Since observations of the discount factor are available, augmenting examine to is The the proxy y to random zero and 2 : 2 i(ct) = - (-a'x) 0(a) = - (-a'x)* - - 2a'q m (32) , and Subtracting m 2 2 does not - 2a' alter population maximization problems. values of the criteria q functions. - m 2 solutions the It (33) . does, The to however, either volatility bounds sample the change the for or maximized Em will be satisfied, and only if if, = £ max aeC s E<p(a) 0, (34) 0, (35) when positivity is ignored, or max aeC when positivity Proposition 2.2 £ E<t>(cc) limiting The imposed. is distribution reported of these hypotheses using sample analog estimators of £ and £. have formulated the plays estimation in (appropriately modified) can be applied to construct a test no problem role so that due to distributions for these limiting the in we Again, approximation error parameter sample analogs. In practice we find the solutions for estimate particular, Then asymptotic the - £•] mean zero and variance the statistic. tests. In This variance can be estimated in the manner u'l^u. Since £ is not specified under the null hypothesis "conservative" choice of £, = is used in constructing the test 7 Similar approaches applied when a instead one-sided form converges in distribution to a normal random variable with described in Section 2.B. (35), and errors, be the maximized value of F (0) over the constraint set C. let c Wl[c standard the sample maximization problems, of time actual to series data. testing a model for In m can be this case of the discount constructed the from randomness of factor can simulated 0(a) be data can be decomposed additively into two components, one due to the randomness of the security market payoffs and prices and the other due to the simulation of ZA m. As in the work of McFadden (1989), Duffie and (1991) Singleton and Pakes and Pollard (1993), (1989), variance asymptotic the Lee and Ingram limiting distribution will now have an extra component due to error induced by simulation. For an example of this the in the sampling approach and a more extensive discussion see Heaton (1993). When the first moments of m can be computed numerically with an two arbitrarily high degree of accuracy, we can proceed as follows. price vector with Em instead of m and subtract Em of m 2 as in (32) and (33). 2 Augment the from the criteria instead This same strategy can be employed to assess the accuracy of the estimated feasible region for means and standard deviations of stochastic discount factors. For any hypothetical mean-standard deviation pair for m, one can compute the corresponding test statistic and probability value. 3.B Minimizing the Specification-Error Bound for Parameterized Families of Models Recall that the specification-error bounds provide a way to assess the usefulness In pricing asset an of misspecif ied. many unknown parameters. situations For example, model the in a even discount when technically is it depends proxy factor on representative consumer model with constant relative risk aversion preferences, the pure rate of time preference and the coefficient of relative risk aversion are typically unknown. case one way specification discount to estimate error. the parameters Alternatively, factor proxy depends on a unknown coefficients. As in in linear model of the an observable is (1987) minimize factor combination of the work of Shanken to the In this model, the the factors with one could selecting factor coefficients to minimize the specification error. imagine We now sketch how the results of Section 2.B extend in a straightforward manner to 25 obtain theory distribution a for minimized the value In Section 4 we discuss distribution specification-error bound. the of theory for the resulting estimators of the parameters of the discount factor. Suppose that the discount factor proxy y depends on the parameter vector € The population optimization problems of B where B is a compact set. interest are now: 5^ 5 2 = min 0eB max aeC = min BeB max aeC 2 - |£y(/3) £y(p) 2 E{{y{B) - x'a) - £{[(y(/3) 2 - 2a' Eq\ } - x'a)*] 2 } (36! , - 2a' Eq] I (37) . > When 5 and 6 are strictly positive and the parameterized family of stochastic discount satisfies factors appropriate the smoothness moment and restrictions, an extended version of Proposition 2.2 can be obtained for the sample analog estimators of 5 and the same as the if solutions Again the limiting distribution will be 8. the population optimization problems were to known a priori. The approach can extended be compare to specification-errors for two nonnested families of models. smallest the Such a comparison potentially can be used as a device for selecting between the two families of Vuong models. large-sample (1989) behavior of examined very a likelihood ratios similar for two problem using by nonnested families misspecified models (in particular, see the discussion in Section 1989); and we can imitate and adapt 26 his analysis to our the 5 of of Vuong problem. More Take the null hypothesis to be: with two such families. (38) Under the null hypothesis, the smallest specification-error associated with As a consequence the performance of each parameterized family is the same. the parameterized two accounted for. This families can not ranked be hypothesis can be tested once using by error sampling the corresponding distribution theory for the difference between the analog estimators of 4. is S Asymptotic Distribution of the Multipliers Recall that the asymptotic distribution f discussed in Sections 2 and 3 depends only on the population solutions to the conjugate problems (8) and other In (9). words, sampling error in the estimated multipliers does not contribute to the limiting distribution of the specification error bounds. However, as elsewhere in econometric practice, the magnitude of the multipliers remain interesting in their own right as a measure of the importance Consequently, bounds. components of is it the of advantageous to pricing be able to relations make to the statistical inferences about their magnitude. To amplify this point, multiplier estimators one use of the asymptotic distribution for the test to is volatility bounds remain the same when analysis. question whether a A special case of such a test of interest is whether given the specification-error is a region subset an initial set of test where the asset returns, additional asset returns result in an increase in the volatility bounds. is problematic to construct a test or subset of assets is omitted from the directly in terms of the It difference between measured a corresponding bound with computed bound with calculated full the more the securities set limited array of and the securities because the resulting statistic has a degenerate distribution under the null hypothesis. This degeneracy follows from the fact that sampling error in the multipliers does not contribute to the limiting distribution for the bounds and is circumvented by instead basing the statistical estimated multipliers. That is, is advantageous it to test directly on the reformulate the null hypothesis to be: Ra = 0, or R a = (39) where R is an appropriately constructed selection matrix (see below), and to use the limiting distribution for the estimated multipliers in constructing an asymptotic chi-square test. Several literature. g versions region of Snow For example, subset have tests been used the in considered the small firm effect by (1991) examining whether the returns on small capitalization stocks have incremental importance in determining the volatility bounds over and above the returns of large capitalization stocks. Other examples can be found in Braun (1991), Cochrane and Hansen (1992), De Santis (1993) and Knez (1993). The limiting applications as distribution well. specification-error For analysis important contributors to for testing instance, is model multipliers the helpful in (39) shows in ascertaining misspecif ication. Also, up in other conjunction which assets with are when a researcher uses the specification-error bounds to select among a parameterized family of discount factor proxies, parameter vector chosen. it is desirable As we will see to in make this inferences section, the about the asymptotic distribution for the parameter estimator selected in this fashion interacts ZS A with distribution limiting the for estimated the multipliers. As a consequence, our characterization of the multiplier limit distribution is an component important in derivation the the of distribution limiting for estimators of parametric stochastic discount factor proxies. The remainder of this section is organized as follows. the distribution theory for the estimated multipliers In Section 4. we comment briefly on how the theory can extended be assuming is developed In Section 4.B that there are no assets subject to short-sale constraints. the to case where short-sale constraints are imposed on some of the assets. 4. A Distribution without Market Frictions In the consequence absence the of short-sale estimation problem constraints, for the the cone multipliers C is is R n . posed As as a an unconstrained maximization problem and the limiting covariance matrices for the asymptotic distribution of the coefficient estimators have a form that is familiar both from M estimation [for example, see Huber (1981)] and from GHH estimation [for example, see Hansen (1982)]. The only complication occurs when considering the bounds in which the no-arbitrage restriction is fully exploited because of the kink induced by the nonnegativity restriction. The moment conditions of interest are given by the first order conditions (10) and (11) for the conjugate maximum problems: E[x{y-x'a) - q] = (40) 0, and E[x(y-x'a) + - q) = (41) . 29 Y^[x(y-x'a - q] ) T = (42) and Ej.txCy-x'a^)* - ql = (43) . While the equations for a are linear, those for a are nonlinear. latter we case, use linear a approximation the to In the conditions moment in deriving the central limit approximation for the parameters: x(y-x'a) - ~ q x(y-x'a) x(y-x'a)l Notice that the - q - xx' 1 {y _ x ,^ 0> function of a on the (44) q side left =0. except at values of a such that y-x'a - .(a-a) ,~ . of is (44) differentiable We assume that such sample points are "unusual": Assumption 4.1: Pr{y-x' a = 0} = As is shown in Appendix C, 0. Assumptions 1.1 and 4.1 are sufficient for us to study the asymptotic behavior of the estimator {a £[x(y-x'ct)l. ,~ .. {y-x'aiO} To use linear £(xx'l. _ /~ >n y) must > using the linearization 9 on the right side of (44) - q] M equation be = system nonsingular. (45) . (45) to Given identify Assumption condition is equivalent to Assumption 1.4 because x and x no short-sale constraints are imposed. 30 The the a, 4.1, matrix this rank must coincide when counterpart to this rank condition for a is that second moment matrix E{xx' the ) be nonsingular as required by Assumption 1.3. Working with the moment linear two conditions, we obtain the approximations: •T(a /T(a - a) * -[Eixx'l^.-^r^T^lxiy-x'*)* - a) ~ -lEUx' T T - q) (46) ))~ 1 VT£ lxiy-x'a) q] i where the notation ~ is used to denote the fact that the differences between the left and right sides of [01]. (46) converge in probability to zero. Let w a Combining approximations (46) with Assumptions 2.2 and 2.3 gives us the asymptotic distribution of the analog estimators. Proposition 4.1: Then {v^T(a -a)} Suppose Assumptions converges in 1.1-1.3, and 2.2 are satisfied. 2.1 distribution to a normally distributed random Suppose Assumptions 1.1-1.4, 2.1, 2.3 and 4.1 are satisfied. Wl{a Then -a)} converges in distribution to a normally distributed random vector with mean zero and covariance matrix: To apply these [Eixx'l. _ /~ >n »)l limiting distributions in wVw' [E{xx' 1. _ /~ >n \)l practice requires consistent estimators of the asymptotic covariance matrices. can be estimated using one of Under assumptions maintained the in The spectral methods Proposition 4.1, terms wVw' vW and referenced previously. the matrices Eixx' ) and E(xx'\. _ /~ ») can be estimated consistently by their sample analogs, where >n the estimator a is used in place of matrices. 31 a in estimating the second of these We now briefly consider two extensions of Proposition 4.1: (i) Estimation of the parameters of a discount factor proxy. that the discount factor proxy depends on the parameter vector be the specification error when positivity the parameter vector that minimizes is Suppose and let Assume that the parameterized family satisfies the appropriate imposed. smoothness and moment parameter space. restrictions, and that in is the interior of the The population moment conditions are given by: E{x[y(0)-x'a] - q> = (47) 0; and e[— (pXyW - [y(£) - a'x] ^30 + = }} (48) 0. > The distribution theory for the analog estimators respectively can be deduced by taking linear {b > and {a approximations > to and a of the sample moment conditions (47) and (48) and appealing to the results of Appendix (ii) assets Region subset tests. under consideration C. Let z denote an (n-1 )-dimensional vector of with price vector s, and let f be the k-dimensional subvector of z including the k-1 asset payoffs that are to be used to construct the bound augmented by a unit payoff. Formally, the region subset test can be represented as the hypothesis: £[z(f'9) El(f'e)* + - s] - v ] =0, = vector of securities z correctly. for a prespecified v , (49) 0. One possibility is to test this hypothesis and the other is to test whether it is satisfied for our previous setup, form the n-dimensional vector x by augmenting z with a unit payoff and form q by augmenting s with the "price" v (49) can be . Then hypothesis interpreted as a zero restriction on the coefficient vector a employed in Sections 1, 2 and The components of coefficient vector a 4. A. set to zero correspond to the entries of z that are omitted from f. sample Wald test this of restriction zero can be formed by A large applying the based on the limiting distribution in Proposition 4.1. Alternatively, we could estimate the overidentif ied system (49) using GMM. parameter vector The analysis leading up to Proposition 4.1 can be easily modified to show that the minimized value of the criterion function is distributed as a chi-square random variable with n - k degrees of freedom [see Hansen (1982)]. When the hypothesis of interest is altered to freedom. 4.B Distribution with Market Frictions We now briefly describe how some short-sale constraints are distribution theory the imposed (C is a is modified when proper subset of IR ) . We will focus on the limiting behavior of Vlia -a), but the results for Vt(a -a) are very similar. As in Section the payoffs with equality or not, Emx = Eq , or Emx < 1, we partition x by whether or not m prices that is by whether Eq . (50) inequality will equal zero with arbitrarily high probability as the strict Hence the sample size gets large. limiting distribution is degenerate for these component estimators. Consider next the estimator of the remaining subvector of denote limiting distribution of the estimator of y separately. the lower-dimensional point of C, to deduce However, be cone associated with estimating a distribution normal limiting if y is at for the boundary of the cone C, function of Haberman (1989), page 1645]. 5. which we y. If the Let C be interior an is y then the argument leading up to Proposition 4.1 can be imitated nonlinear a a, Because of the degeneracy just described, we can, in effect, treat 7. a normally the estimator. parameter the limiting distribution may distributed vector random [see 10 Conclusions and Extensions In we paper this provided statistical methods assessing for asset-pricing models based on specification-error and volatility bounds. Two significant advantages of the statistical methods are that they are easy to interpret and they that are simple to implement transactions costs and short-sales constraints. variety of ways. For example, the discount factor, to examine even in the presence of The results can be used in a they can be used to test specific models of the information contained in different sets of asset-market data, and to assess misspecified asset-pricing models. There are several interesting extensions of the econometric methods in this paper including the following: (i) The short-sale constraint "solvency constraints" formulation could be generalized whereby portfolios are restricted so 34 that to include portfolio payoffs nonnegative. are This As in Section imposing to form a of borrowing Hindy (1993) and Luttmer (1994)]. constraints on portfolio weights the 1, amounts for example, constraint on consumers [see, the in presence of solvency constraints can be formulated as a closed convex cone. However, without knowledge of the distribution of the payoffs on primitive securities the cone would be subject to estimation error and hence not directly covered The consistency proof in Section 2.C for the by the results in this paper. arbitrage bounds might well more generally. It errors constraint for the is adaptable be then interest of sets approximating constraint to how understand to impact on approximation distribution the sets of the for the specification and/or volatility bounds. (ii) difficult A feature of limiting the distribution theory Lagrange multipliers in the presence of short-sales constraints (Section 4.C) is the manner associated harder compute to in which it depends discontinuities. use in example Wolak bounds on in other parameter true makes has test of vector and distribution the settings, probabilities and Boudoukh, (1991) the feature This practice and, approximate on led Richardson and Smith theory researchers statistics (1992)]. the [see, to for Perhaps similar probability bounds could be derived for the region subset tests with frictions. (iii) Using tools similar to those described in Section 1, (1995) have integration. should be incorporate developed possible nonparametric to transactions extend costs the in measures econometric the propose. 35 market of market methods in integration Chen and Knez this paper measures It to they Appendix Consistency A: In this appendix we demonstrate formally the results of Section 2. A, We maintain Assumptions 1.1-1.3, and 2.1 throughout. 2.D. Let n denote a compact set in 11 denote the closure of subsets of 11. t)(/i For any subset h of . K denote Let h. IR tj - a ,/i ) = max{ sup a eh inf I a on |, 2 X given by sup a eh 2 to define notions of convergence of compact sets. use construct the of a lim we let cl(h) 11, the collection of all nonempty closed We use the Hausdorff metric a eh 112 will and sup of a inf a eh I - a a |> . (A.l) 11 2 For some of our results we sequence in We K. follow Hildenbrand (1974) and define: Definition A.l: For a sequence {h > in 11, lim sup h Since the sets, it is closed and not empty. lim sup is the = n cl » J J ( u h J2*> ) J intersection of a decreasing sequence of closed An alternative way to characterize the Jim sup is to imagine forming sequences of points by selecting a point from each h . and, All of the limit points of convergent subsequences are in the lim sup, in fact, all of elements of the lim sup can be represented in this manner. We shall make reference to an implication of a Corollary on page 30 of Hildenbrand (1974) that characterizes the set "approximating" function over an "approximating set." 3(3 of minimizers of an Suppose Lemma A.l: {0 (i) is } sequence of continuous functions mapping a converges uniformly to ip 1/ into R that ; and {h (ii) converges to h } Then Jim sup g and iim min °° = </< = {u e h : (u) \p ) for all u' € h J . CO °° denote the set of positive integers augmented by usual metric for a one-point sequence in {</> of (ii), the sequence {h in } conjunction with h then Turning 1 follows from the Corollary of page 22 in Hildenbrand. to the result in Sections the (i), defines a continuous function on } continuous compact correspondence mapping } into Proposition let } and endow £ with the +oo, Then in light of compactif ication. in conjunction with } light Al }, J To verify that this follows from the Corollary in Hildenbrand, Proof: Lemma (u' \p h J and i J J J min Jt h where g c g J x 11; defines a The conclusion of the Ii. together with part (ii) of Q.E.D. 1 and 2. A, we first establish the compactness of the set of solutions to the conjugate problems: Lemma (9) A. 2: The set of solutions to conjugate maximization problems are compact. 37 (8) and consider Proof: We problem (8) constraint is set the case The similar. set and closed is problem of The proof (9). solutions of criterion the for closed is function the case because of the continuous. is Boundedness of the set of solutions can be demonstrated by investigating the We consider two cases: directions tail properties of the criterion function. < for which which (9) <;'x £' x is negative with positive probability and directions is nonnegative. and divide it by 1 + for C, To study the former case we take the criterion in |a| 2 For large values of . |a| the scaled criterion is approximately: - Hence |<| payoff in E[(-x'0 +2 ] where < Consequently, P. Consider next 1.2 we identically zero. When that |a| 2 1/2 ] (A. 2) . Moreover, |a|. unsealed criterion will the x is a C,' decrease (to -co) |a|. directions have a/[l + large values of is approximately one for quadratically for large values Assumption = C,' <;'x = 0, C, for Eq must it which be C,' x is nonnegative. From strictly positive unless C,' x is follows from Assumptions 1.2 and 1.3 that C' Eq is again strictly positive. For directions ^ for which the payoff C,' x is nonnegative, tail behavior of the criterion after dividing by approximately - <'£q for large values of |a|. (1 + |a| we study the 2 1/2 ) , which yields Hence in these directions the the unsealed criterion must diminish (to -») at least linearly in |a| . Thus in either case, we find that the set of solutions to conjugate problem (9) bounded. Q.E.D. We now formally establish Proposition 2.1: is Proof of Proposition 2.1: We treat only the for {d very is > cc Assumptions similar. converges almost surely to E$(a) concave as is s N> |ot| set in 2.1 imply and D = C {a e IR from Lemma Further . : I a = I Then C N>. maximizers of and D N we have surely, in D be the maximized value of 5 < By the statistical arbitrage {£>} converges the A. 2, are of set {a € C : By compact. the maximizers of T T, turn results the to consistency of bounds A 4> Lf v <p} on C that compact explore "directions set for to the choice infinity." variables study We on C almost are also not follows that for } to 5 follows from the Q.E.D. Section in Recall . . it 2.C and {£ > in investigate and arbitrage the representable as solutions to linear programming problems. natural E<j> coincide with those over over C analog estimators sample and Then by 3 choice of N . N the maximizers of £_0 over C almost sure uniform convergence of {T now is contains all of the converges uniformly to {Y ^} the almost sure convergence of {d Consequently, We over D convexity of C and concavity of sufficiently large C. Since 6. for sufficiently large T, . Ed> r N that 70 over the constraint set C and that none of the maximizers E4> Let 5 . {Yiioc)} T, define C choosing N to be sufficiently large we can ensure that C are in D that Since for each For a positive number N, is bounded. E4> and Theorem 10.8 of Rockafellar implies that E$, uniformly on any compact maximizers of 1.1 each aeC. for these these {u > for bounds the the are Since there is no problems, "directions" we must using a compactif ication of the parameter space. First consider any a e C such that with probability one a'x £ -1 for all a' t x £ -1 with probability one. with probability one and Then (aTq) < I u-'Tji' ^ follows sup lim that * I To construct a compact parameter space, we map space for each problem into the closed unit ball in R We consider explicitly the case of u with A the n completely analogous to the case for u one. parameter original which we denote as the case of The proofs for . probability I II. are and are omitted. Notice that the constraint set used in defining v can be represented as the set of all a € C satisfying the equation: £[(1 - a'x) + ] = (A. 3) . As in the proof of Lemma A. 2, we map the parameter space into the unit ball (with a slightly different transformation). maps R n into open unit the ball. The transformation < = a/(l+|a|) compact if y To the transformed space, we consider adding the boundary points of the unit ball. we can recover the original parameterization by considering parameter Notice that the inverse mapping: a for |<| < 1. = C/(l This (A. 4) |C|) Using the transformation in a's that satisfy D* " = (A. 3) { we consider: < e llnC transformation instead of considering those (A. 4), | £{[(1 - |<|) - potentially adds x'0 solutions 40 + = > to } (A. 3) (A. 5) . by including the boundary of the unit ball. for which x' C, £ 0, The potentially problematic values of C are those and C,eC = |<| We rule this out by limiting attention 1. to values of < in (A. 6) effect by focusing on £'s in payoffs with "high" prices. D we are eliminating concerned with estimated upper arbitrage bounds Also, high. any < in D for which is nonpositive. Lemma Proof: T)(D ,D) First |<| ) = |<| notice that < 1 corresponding Fq since are that - x'C,]* on U. 1) Note that - x'cj + - s n D converges too to D c Eq n almost We next establish that 0. show that T [(1 e||[(1 - IC 1 low, not too - 11 |^|) - x' C,] Hence, from Lemma A.l, the . D. surely, lim D then = D . converges uniformly to n C is compact and that: [d - K2 D (1 + (£|x| + - *'V (A7) l| 1/2 2 ) )K r C z |. This is sufficient for the Uniform Law of Large Numbers of Hansen (1982) apply. to must have an (average) price that Then lim sup D oo. converges almost surely to To do this we first £[(1 - s This eliminates the troublesome points (directions) from D Suppose that u A. 3: C,' This does not cause us problems because we are to lim sup of the sequence of minimizers of - T [(1 - ICU - x' - x' <;]* I<l) over C.) 11 Since v . minimizers of £[(1 must also be in D - n C is contained in the set of minimizers of £[(1 < oo, *'<]*. - |<|) the set D for all Til. is not empty and D With probability one, Since D is separable, the set of is any point in D a common probability First note that Proof: = mini u C'Ej-g/d-lCN < € D I n D t > t for sufficiently large T, (A. 8) and in smaller values of constraint set Lemma A. 2 to D n Lemma A. 5: Proof: D. the maximized criterion. For instance, augmented to include all of the points in D is suppose n the Then D. implies that this sequence of augmented constraint sets converges The conclusion then follows from Lemma A.l. Suppose that v Since v = o probability one. oo, = oo. Then iu > Q.E.D. diverges with probability one. there are no values of a € C such that a'x £ Consequently, the only values of £ in D 1 with are ones for which Kl = First suppose that D We consider two cases. 1. - convergence of ^[(1 sufficiently large T, - |<M to £[(1 x' C,)* = a and u D = <x>. - |<|) - = a. + Next suppose that D there are no arbitrage opportunities (Assumption 1.2), C'Eq D such that ll^'xll > e , it = inf{C,'Eq follows large T, CI_<7 C,' Eq for any < > : C, € D* } > from Lemma > A. * n = II<'jcII 0. (A. 9) converges almost surely to for The convergence of {D . > sufficiently to D coupled have norm one then implies that {u > Q.E.D. Taken together. Lemmas In such that with probability one that 1 c/2 for all £ e D diverges almost surely. B: D* in . with the fact that all elements of D Appendix for any C > is closed implying that Since {Y q} converges to Eq almost surely and D D Since * 0. Also, Assumption 1.2 together with the no-redundancy 0. Assumption 1.3 imply that Furthermore, D The uniform implies that for x' <] A. 4 A. 3, and A. 5 imply Proposition 2.3. Asymptotic Distribution of the Bounds Estimators this appendix we show that in the case in which the prices of the payoffs are constant, the asymptotic distribution of the estimated bounds can be demonstrated even when the parameter vector is not uniquely identified (even when Assumption 1.4 is not satisfied). Proof of Proposition 2.2: We consider the case of d set of maximizers of Y 4> an d l . et h The case of d is similar. Let h be the set of maximizers of £#. be the For each let T, be a measurable selection from h a Since lim sup h page 54). (1974), there is a sequence {a a € h h , q = £{y(y-a'x) a' + (y-a'x) - consider the decomposition of /IT v'T[(5 2 - I ) +2 -a A. =0 \ 2 } t = Hi ldenbrand /IX^U^ [ (d compact, is almost surely (see of Hansen and Jagannathan 1 + (y-a'x) . implies that for (9) so that a' q is the same for all a € >, the random variable 0(a) As a result, . \a the complementary slackness condition for problem Also, of result in the same random variable m = that all a e h is 1 almost surely and h Further, an implication of Lemma Appendix A). (1991) = h such that lim in h } Theorem (see - 5 ) - 4>(a )] + r is the same for all a € h Now . as in (23): ] VT^[4>U - ) t E4>U r (B.l) )]. As in relation (26), we have: s s VTj^lila^ - 4>U t (B.2) )} , V TX [(mx - q) - E[mx - q))-{a^ T Since \a -a Appendix C: In | this converges almost surely to 0, - aj . the result follows. Q.E.D. Asymptotic Distribution of the Multipliers appendix consider we the asymptotic distribution of our estimator of the Lagrange multipliers when there are no transaction costs. We begin by demonstrating that restrictions used in Hansen can be (1989) to (1982) extended along the lines of Pollard (1985) and Pakes and Pollard accommodate "kinks" in the functions used to represent the moment conditions. We then show how to use this result to prove Proposition 4.1. The notation used in our initial proposition for GMM estimators conflicts with some of the notation used elsewhere in the paper. denote the parameter vector of interest and underlying parameter space T. We let any hypothetical point in the The parameter space is restricted to satisfy: Assumption C.l: T contains an open ball in IR about We will use the construct of a random function. . A random function ip maps the set of sample points into the space of vector-valued continuous functions on T. We require that ^(0) be an n-dimensional random vector for each in T. We also consider an approximating function The composite random function satisfies: that is linear 0. Assumption C.2: { (i/» ' ,\Jj*' ) ' } is stationary and ergodic and has finite first moments. We now specify the sense in which approximation error induced by using is r t (0) = |0 (0) t - 0*O)I is required to approximate \p \p in place of \p ip . The is • Define: Note that dmodA-) is monotone in 6. 45 Therefore, we can take almost sure We impose the following restrictions on mod limits as 5 declines to zero. Assumption C.3: lim dmod (8) = 5*0 Assumption C.4: Eldmod AS)] The approach adopted < in almost surely. <*> for some 5 Hansen continuity of the derivative of . > (1982) 0. is to restrict the modulus of to converge almost surely to zero and to ifi have a finite expectation for some neighborhood of the parameter. It follows from the Mean-Value Theorem that restrictions imposed in Hansen (1982) on the local behavior of We use ip imply Assumptions C.3 and C.4. Assumptions - C.3 stochastically differentiable. c(8) = sup <\Zj?lt(P) C.4 to study the sense in which T^ is Hence look at the approximation error - E^'OH/I/HM : ie-3 l<5,0*0 o > . o By the Triangle Inequality we have that c(5) £ ^.dmod(5) Thus by Assumptions C.1-C.2, we have that lim lim sup c (5) 5* o t-x» ^ lim Edmod{8) 5* o 4b (C.l) 0. This in turn implies stochastic differentiability condition because the counterpart to c (5) (1985) •TI0-0 |/(1 /TI0-0 + o in the implies (C.l) monotone in in Pollard's which is less than one. |), Also, taken limit in Pollard's Therefore, 70 ~ E,P because c is stationary and {Y A-£A> ergodic, satisfies the stochastic given by 7A-EA. differentiability condition with derivative at is condition The differentiability of limiting moment function £0 follows 6. directly from Assumption C.4. {*/!.} iterated limit the o the Pollard in condition is scaled by converges surely almost Since to zero hence the derivative is asymptotically negligible. Next we function can also function This rank . be by 0* Since the approximation of viewed as a identification local is this condition local, condition on the original . condition differentiability condition identification condition on the approximating impose a global (iii) on the conditions Theorem in derivative already 3.3 of together established Pakes and with imply Pollard discussion on page 1043 of Pakes and Pollard). »A* (b T ) = o combination of moment conditions to be used in estimation. 47 the the stochastic equicontinuity (1989) (see the Assumption C.6: {b Assumption C.7: } {a converges in probability to 6. probability to } converges in a nonrandom matrix a where a £A is nonsingular. Finally, to obtain a limiting distribution for {b Assumption C.8: {/T£_.0O )> converges } we assume: distribution in to a normally distributed random vector with mean zero and nonsingular covariance matrix Sufficient conditions for Assumption C.8 described Gordin approximations as Hansen (1985). This condition implies that by can be and Hall (1969), E^O obtained using martingale ) Heyde is equal (1980) and to zero. The following extension of Theorem 3.1 in Hansen (1982) is now a direct consequence of Theorem 3.3 and Lemma 3.5 in Pakes and Pollard (1989). Proposition C.l: , {V T(b_-£ )> Suppose Assumptions that C.1-C.8 satisfied. are Then converges in distribution to a normally distributed random vector with mean zero and covariance matrix [a o £(A,)] t aV a ooo ' [E(A to ' )a ] Estimation of £A follows as in Hansen (1982) as long as A can be expressed in finite first moment for some 5 probability to £A. > 0. In this case, {F D(b )> converges in Proof of Proposition 4.1: In light satisfies (44) we now verify that of Proposition C.l, Assumption C.3. r(a) Let denote our approximation in random approximation the error: r(a) It |x(y-x'a)(l. J in ,-l,{y-x ,-\. n JI aiO} {y-x'aiO> = , (c2) • follows from the Cauchy-Schwarz Inequality that r(«) Vio} * l'(ri'«)llli^ (l0) s #~ „»)l |xx'a - xx'a||(l, ny -l, {y-x'aaO> {y-x'a^O} y-x'a - , where the second inequality follows because whenever (c 3) )l and y-x'a have opposite |x'a - x'a| dominates |x(y-x'a)| Therefore, signs. the random approximation error satisfies: r(a)/|a-a| 2 s (C.4) \x\ for a * a implying that the modulus of differentiability dmodic) is dominated by |x| positive value of = 2 c, sup{r(oc)/|a-a| |a-a| < e |a-a|<e, for a*a> (C.5) Combined with Assumption 1.1 this implies that for any £[dmod(E)] ~ _, = except when 1, e {y-x a=0} that : and 1, _ . = finite. this case In 1. , is 1 As c it so that r(a) 49 is = * 0, dmod(c) goes to zero possible to choose a such |xx'|. However Assumption 4.1 with probability zero implies that this occurs to zero. converges almost surely Q.E.D. 50 Formally C 2 is the dual cone of C. A weaker version of Assumption 1.3 this more does restriction would replace Eq by than eliminate redundant In q. securities. effect, It also precludes cases in which distinct portfolio weights give rise to the same payoff, with possibly different prices but the same expected prices. 3 Hansen and Jagannathan (1993) showed that the least squares distance between a proxy and the set an alternative M of (possibly negative) stochastic discount factors has pricing-error interpretation: Formally, the interpretation for the least squares problem (6) is inf mzM sup peP 2 £p =l \Emp - Eyp\ and for (7) is inf sup mzM* peH \Emp - Eyp\ 2 £ P =1 where H is the set of payoffs on hypothetical derivative claims. 51 pricing-error ' Assumption 2.1 could be weakened in a variety of ways, but it is maintained process { (x. ,q. More simplicity. pedagogical for ' ,y. )} might we generally, is asymptotically stationary, the stationary distribution of (x'.q'.y) given is that the where the convergence to sufficiently fast to ensure that the Law of is In this case, Large Numbers applies to averages of the form (17). distribution imagine by the stationary the joint point limit of the The Hausdorff metric is usually employed for compact sets to ensure that the resulting distance is Because finite. of vertical the character of the regions and the existence of finite arbitrage bounds, the Hausdorff distance will be finite even though the sets are not bounded. The Euclidean distance could be replaced by the square root of a quadratic form in the in (30) differences between two points as long as a positive weight is given to both dimensions. Even making if hypothesis (35) is satisfied, implementation problematic. the This outside the estimated arbitrage bounds. sample analog may be happens when infinite, sample the mean is This phenomenon does not arise for hypothesis (34). 7 Burnside (1994) alternative and Cecchetti, versions costs are introduced. from positivity and of the Lam and Mark volatility bounds (1993) tests developed and studied when no transactions The test used by Cochrane and Hansen (1992) abstracted can be formulated equivalently using <p in (34). Burnside (1994) for a Monte Carlo comparison of various volatility tests. 52 See g The impetus for this work was the econometric discussion in an unpublished precursor to this paper: Hansen and Jagannathan (1988). 9 Our formal derivation of and Pollard (1989). 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