DEWEY, MIT LIBRARIES 3 9080 02874 5179 Massachusetts Institute of Technology Department of Economics Working Paper Series CAPITOL INCOME TAXES WITH HETEROGENOUS DISCOUNT RATES Peter A. Diamond Johannes Spinnewijn Working Paper 09-22 July 14,2009 RoomE52-251 50 Memorial Drive Cambridge, This MA 02142 paper can be downloaded without charge from the Paper Collection at Social Science Research Network http://ssm.com/abstract=1434182 Capital Income Taxes with Heterogeneous Discount Rates^ Peter Diamond* Johannes Spinnewijn* MIT MIT July 14, 2009 Abstract With heterogeneity in Stiglitz result that savings both skills and preferences for the future, the Atkinson- should not be taxed with optimal taxation of earnings does not hold. Empirical evidence shows that on average people with higher higher rates. skills save at Saez (2002) suggests that with such positive correlation taxing savings can increase welfare. This paper analyzes this issue in a model with correlation between ability and preference the same earnings number to the analysis is level, the that types switch to a lower earning job. who for the future. of types of jobs in the less than perfect To have multiple types economy is restricted. at Key value future consumption less are more tempted to We show that introducing both a small savings tax on the high earners and a small savings subsidy on the low earners increase welfare, regardless of the correlation between ability and preferences However, a uniform for the future. savings tax, as in the Nordic dual income tax, increases welfare only is sufficiently high. results *We There are also some results if that correlation on optimal taxes that parallel the on introducing small taxes. Keywords: Optimal Taxation, Capital Income, Discount Rates JEL Number: H21 Classification Emmanuel Werning and seminar parand the NBER for valuable comments, and the National Science Foundation for financial support (Award 0648741). The research reported herein was supported by the Center for Retirement Research at Boston College pursuant to are grateful to Jesse Edgerton, Louis Kaplow, ticipants at MIT, Saez, Ivan Berkeley, Stockholm University, the Stockholm School of Economics a grant from the U.S. Social Security Administration funded as part of the Retirement Research Consortium. The findings and conclusions are solely those of the authors and should not be construed as representing the opinions or policy of the Social Security Administration or any agency of the Federal Government; or the Center for Retirement Research at Boston College. of Economics, E52-344, 50 Memorial Drive, Cambridge, department 'Department of Economics, E51-090, 50 Memorial Drive, Cambridge, MA MA 02142, pdiamond@mit.edu. 02142, jspinnew@mit.edu. Digitized by the Internet Archive in 2011 with funding from Boston Library Consortium Member Libraries http://www.archive.org/details/capitalincometaxOOdiam Introduction 1 The Atkinson-Stiglitz (1976) theorem shows that linear earnings taxes, optimal taxation assumptions are tween consumption and labor and the available tax tools include non- inconsistent with taxing savings when two key consumers have preferences that are separable be- (1) that all satisfied: is when (2) that all consumers have the same sub-utility function of consumption. Empirical evidence suggests that on average those with higher (Dynan, Skinner and Zeldes, 2004, Banks and Diamond, 2008). at higher rates relax the second condition skill skills We therefore and analyze the taxation of savings with heterogeneity We and savings propensity. save both in consider both uniform and earnings-varying taxation of savings. This paper uses a simple model restricted. This sheds light on the role of the positive correlation argument we skill and the is be taxed, whereas the savings of the low independent of the correlation between ability optimum has factors, provided that the A is of savings progressive in earnings. In a two-skills model, earners should be subsidized. This result productive job. economy and savings propensity. The paper provides an find that the savings of the high earners should and discount in the desirability of earnings-dependent savings taxes between making the taxation for which the number of types of jobs in the high skilled workers on the more uniform savings tax, however, only increases welfare if that correlation is sufficiently high. Our paper builds on the analysis Saez (2002). He derives conditions on endogenous in variables to sign the effect on social welfare of introducing a uniform subsidy, when consumers have heterogeneous an optimal non-linear earnings net marginal social value is restricted to the same on savings increases welfare if or a With sub-utility functions of consumption. tax, a small tax either the negatively correlated with savings, conditional on earnings, or on average those who choose to earn if commodity tax earnings. less By save less than those restricting the the importance of the (exogenous) correlation between number skills who choose to earn more, of types of jobs, we analyze and savings preferences for the taxation of savings. Primary attention and two skill levels. screening problem. is focused on a model with four worker types Thus we The model assumes model where each worker can setting are examining a particular with two discount factors example of a multidimensional the existence of two jobs, rather than the standard select the where workers with the same - skill number of hours to be worked. 1 This results in a but different discount factors choose the same job and so have the same earnings. With the introduction of earnings-related savings tax : A limited number of jobs was assumed in Diamond (2006). rates, We they are subject to the same tax rates. assume that optimum both at the high-skill types work at the high-skill job and that redistribution from high earners to low earners is Given these assumptions the important redistribution. social welfare increases with the introduction of a tax on the savings of high earners and with the introduction of a subsidy on the savings of low earners. The relative frequencies of the four types in the population plays no role in the derivation of this result, conditional on the assumed structure of the optimum. The underlying assumption is that those valuing the future work than those valuing the future less, more are more conditional on the disutility of work. This that an incentive compatibility (IC) constraint just binding on a high value for the future not binding on a high is willing to skill worker with low skill worker with high value Earnings-dependent taxes and subsidies on savings allow an increase for the future. tempted to switch jobs. all are high earners) eases the binding IC constraint transfers resources from the high saver to the low saver for it who In particular, introducing taxation of savings of high earners (and transferring the revenue back equally to since by in redistribution targeting types in a given job with saving preferences different than those of types just means whom the IC constraint binding. Introducing a subsidy on savings for low earners (financed by equal taxation on low earners) also eases the binding IC constraint by making switching to the lower job is all less attractive to the high earner with low savings. In extensions, the case for taxing the savings of high earners appears to be earners. more robust than the case While the focus of the paper is for subsidizing the savings of the introduction of small taxes, we low also consider optimal taxes under stronger assumptions. 2 The assumption is in line that those with less discounting of the future are with standard modeling, representing preferences by u (x) alternative specification j-u (x) types with higher 5 + u (c) — v (~/n ; ) prefer to save more, but to l + more S,u (c) willing to — v work would imply the exact opposite. That work less. We on education and is, examine some empirical support for our assumption, using data from the Survey of Consumer Finances (SCF). find that conditional An (z/rii). We age, people with higher discount factors tend to earn more. To proxy for the discount factor, we use reported savings and the time horizon people report having in mind when making spending and savings to revisit the positive correlation between skills decision. We also use these proxies and savings propensities. This paper contributes to the literature on the optimal choice of the tax base and the joint taxation of labor and capital incomes in particular. Banks and Diamond (2008) review the literature on the inclusion of capital income in the tax base. The analysis assumes rational savings by relevant for retirement savings policies. all Gordon (2004) and Gordon workers. Concern about too little individual savings is also and Kopczuk (2008) argue that capital income reveals information about earnings thus should be included in the tax base. people with different an income tax, skills may be and ability and Blomquist and Christiansen (2008) analyze how different preferences for leisure separated with a commodity tax. who cannot be The separated with four-types model with hours chosen by workers has been studied by Tenhunen and Tuomala (2008), which calculates a set of examples, but explores the analytics only in two- and three-type models. We both welfarist and paternalist objective functions. We examples to some of our results below. in a two-types They consider relate the results in their calculated focus on the four-types model since the result model, while striking, does not seem relevant for policy inferences. 3 While the focus of this paper is on capital taxation, the intuition generalizes to the taxation of other commodities for which the preferences are heterogeneous, since this heterogeneity may impact the labor choice as well (Kaplow, 2008a). The paper two jobs. is Section 2 sets up the model with four types and organized as follows. Section 3 characterizes respectively the referring to best and the restricted first no taxation of savings and an 'equal job, equal pay' restriction. first best, Section 4 introduces incentive compatibility constraints and characterizes the second best including Optimal savings tax rates are the introduction of earnings-varying savings tax rates. considered. also Section 5 considers a uniform savings tax, rather than one varying with the level of earnings. For comparison, Section 6 reviews a two-types model. Section 7 discusses empirical support for the assumptions and Section 8 has concluding remarks. Model 2 We consider a model with two periods. Agents consume in both periods, but work only in the first period. Preferences are and work. Denoting earnings by z, first assumed to be separable over time and between consumption period consumption by x, second period consumption by > 0,u" < u' producing output factor We and preferences satisfy U(x, with c, and z. An v' > c, z) 0,v" = > u (x) 0. + An 5u (c) — v (z/n) agent's ability , n determines the disutility of agent's preference for future consumption depends on the discount 5. consider heterogeneity in both ability n and preference for future consumption 5. ''Kocherlakota (2005) provides an argument for regressive earnings-varying wealth taxation. He analyzes skills, which is not present in this model. a model with asymmetric information about stochastically evolving Although robust insights for optimal taxation have been derived in models with two types, considering heterogeneity in two parameters in a model with two types implies perfect cor- between the two parameters. The inference based on a simple two-types economy, relation although simple, we consider a fij may therefore be misleading. and welfare- weights factors 6 and 1 We four-types model. and with Sh Sh, The rj^. > Si. In order to allow for imperfect correlation, denote the four types by ll,lh,hl,hh with frequencies first two types have low ability ni, but differ in discount The second two types have high also differ in discount factors Si and rih factor hh hi lh 11 low ability ni in the economy, h and The /. The output from a job high-ability types can hold either job. redistribution to the low-skilled types balanced that all is > n-i, Si of the worker's type, while the disutility of holding a job varies with ability. types can only hold the low job. n/, low discount factor Sh There are only two jobs , Sh. high discount high ability n h with ability sufficiently is independent The We low-ability assume that important and the type mix sufficiently high-skilled workers hold high-skilled jobs at the various optima analyzed. This requires a restriction on the weights in the social welfare functions and the population distribution, We which we do not explore. begin with the produced on a job The first is first best, the same which for differs everyone holding the job. best has the property that there consider a restricted first best (the term constraints, the term 'restricted' from the usual treatment 'first is We in that the assume a output linear technology. no marginal taxation of savings. Then we best' refers to a lack of incentive compatibility means limited tax tools, but not limited by IC constraints) with zero taxation of savings and the requirement that everyone holding a job receives the same pay (no taxes based on social welfare We identity, only on potential earnings). We calculate whether can be improved by taxing or subsidizing savings. then turn to the second best, with taxes based on earnings, not potential earnings, so that there is an incentive compatibility constraint. restriction, thus preserving the condition of equal potential gains from taxing or subsidizing savings. pay We assume a zero taxation of savings for equal work. Again we ask about — First Best 3 In the is first worker best, each is assigned to the matching job and the social welfare function maximized with respect to the consumption type-specific With the periods and the job-specific output levels, subject to a resource constraint. weight of type of ij i] , t the first and second levels in the first welfare best solves: £ /y^j (u Maximize I|C ,, + [xtj] 6jU - [cy] v {z l /n,}) (1) subject E+ to: ^2 fij i x ij +# Forming a Lagrangian with A the Lagrange multiplier £ = Yl f*rt*i u ( ^+ ~ Si u fad v \ Zl l _1 type ij ~~ < z%) the resource constraint, for n^ ~ A 5Z fa ( Xii +R ' lc H ~ we have z i) i,j hi We cy define the net marginal social value of first period consumption for an individual of [xij] - as 9ij Along the relevant portion of the gij = + VtjU A. social welfare optima, and u v' ifulu = [zi/nA L fihVih) [x^] = = (/« 5jRu' + fih) [cy] A = we have the for all i,j, fuVuu' and + [xu] following properties: fihVih.u' [x ih ] , rii for both the high-skilled and the low-skilled jobs. The net marginal social value of first period consumption for each type equals the required output for a given job and the saving of each type is is undistorted. Given that independent of an individual's type, the earnings are marginally distorted upward for one discount- factor type and downward for the other type, since v! [xu] ^ u' [x^], unless the welfare weights satisfy T] d = >] lh . The output is undistorted 'on average' though. 3.1 Equal Pay Restricted First Best: for Equal Work and No Taxation of Savings If the (after-tax) earnings on a job, y ; , is restricted to be type- independent and savings can not be taxed, there are further constraints, which we approach using the indirect utility-of- consumption function, This function R\. iuj [y, u>j [j/j = R] subject satisfies max u x to: [x] + R~ 1 c + 5jU — y. [c] For later use, we note that dwj u \x] dy j£ where Sj [y, We all R] is = R- 2 cu'[x} = R- (y-x)u'[x} = R-h J 1 iy,R}u'[x} the savings function of someone with discount factor 5j. continue to assume that the welfare weights and population fractions are such that high skilled are on the more productive job at the optimum. The restricted first best solves the following problem, Maximize^ ]T fljrjij ( Wj R] [y n - v [zjn,]) (2) subject E+ to: J2 fij (Vi ~ zi) < Forming a Lagrangian, we have hi hi The first order conditions (FOC) are 5Z fctfijU' [Xij] = A^/y 3 Yl fitful 3 \ zil ni\ l n i = A 3 for i — h, I. 5Z^' 3 Recalling the definition of the net marginal social utility, g tJ = rj^u' [xij] — A, the population-weighted values add to zero at each job, }] fij9ij = for i = h,l. 3 Thus, the welfare weights determine the direction of desired redistribution (given the equal pay condition) between workers on each job. Also, vl [xij] The FOC for job outputs, z,, are the = 5jRu' same absence of savings taxation, in the for all i,j. [cij] as given above. Restricted First Best with Small Earnings-Dependent Savings 3.2 Taxes Given the observability of earnings, small linear taxes on savings (collected in the first period) could be set differently for high and low earners. This can for instance be implemented by IRA and the rules on retirement savings accounts, like the desire to redistribute can be met by a small 401 (k) in the US. them by (local) on savings by workers on linear tax or subsidy a given job with the revenues returned equally to The raising net-of-tax earnings on the job. Differentiating the Lagrangian with respect to a savings tax rate r, level i/i, evaluated at a zero tax = A ( d7~ The impact H of a savings tax level: fa (tt ?/i, the derivative can be written = -fr ~ xv) H fvW' ) on the Lagrangian revenue constraint and the impact on by on those with earnings 11 fa utilities. is made up Using the \ x ij\ of FOC (Vi two ~ x u) • pieces: the with respect to impact on the j/j, multiplied as: (%'"' (^ ~ A ) X 'J = 11 fa9U x H- 3 3 Recall that Hfij9ij = for i = h J- 3 This implies that a tax on the savings by the two types on a given job increases welfare the savings of the one type towards which redistribution compared The is desirable saves sufficiently if little to the other type. welfare weights imply the desired direction of redistribution within productivity types and so the signs of g }J With equal incomes and . > Cih Thus, if first period utilities get Cu the same weights for both types, n il implying a desire to redistribute to the high saver. In contrast, the same weights for both types, redistribute to the low saver. we have rj hh u' [xhh] = Vm u given discount factors, i] ' ht \ If x m} = r) we have different discount factors, if = r) lh , < gu second period < g,h, utilities get u Si = n lh 5h, the signs are reversed, implying a desire to there is no desire to redistribute for high (low) skill types m general, with uniform weights for i] {Vih u ' l — x ih} Va u> x u})\ u we do not satisfy both conditions. , Second Best 4 We draw a distinction between restricted first-best analyses and second-best ones based on the absence or presence of IC constraints involving taking a job with lower productivity (the reverse having been ruled out by assumption). observability of productivity. IC constraints are binding. The prime We is, the distinction depends on the issue in second-best analyses is determining which start with the further restriction, as above, that savings not be taxed. With no taxation of savings and equal pay imitating the other discount rate type if That who is for equal work, the IC constraint of not holding the same job does not bind. Similarly, a high productivity worker were to take the low productivity job, the person imitated would be the one with the same discount need not be such a worker for a high skill factor. Imitation is a misnomer here since there worker to optimize savings while taking a low skill job given the assumed policy tools and information. We add the critical assumption that earnings distribution issues are that at the second-best period consumption g tJ optimum = sufficiently important (with IC constraints) the net marginal social value of r/^u' [x l j] — A is first negative for both of the worker types holding the high-skill job and positive for both of the types holding the low-skilled job. Without a binding IC constraint, this condition could not hold at the optimum as noted above. Assumption 1 The net marginal 9hj social values of first period < ®,9ij > 0, for j -h,l. consumption satisfy We No Second best with 4.1 Taxation of Savings assume that the Pareto-weights and population fractions are such that workers work at the high-skilled job and the desired is sufficient that at least one IC constraint Maximize,,,, subject J2 f^q^ E+ to: Wh wi Forming a Lagrangian with and assuming that C = Y fan ( WJ at the t y" - v R] ~ v [yh, -v R] ~ ~0 < fij {Vi [yh,R] ° ] ( wh /n h > W[ [z h \ [yh R] R] [yu -v - 3) [zi/n h ] v [zi/n h ] . the Lagrange multiplier for the corresponding IC constraint, fj,j v l ] [zjn,]) /n h > [z h optimum each worker R ~ level of redistribution to lower earners binding. is (vjj [yi} J2 high-skilled all Zi / n^ - A Y i,j assigned to the matching job, is fa ( y > we have ~ *) hi + 22 ^j wj ( [ y/" R ~ _ w i v z >J n h\ ] [ \y<-> R + ] v z i/ n h]) [ 3 Since the first-period consumption of type hj period consumption of type the Ij, Y fWhj u Y ' [ FOC switching to the low job equals the if with respect to earnings are YW -Y x hj] + [xhj] ~ X j ; hsiij 11 ' [ x ij] Y Ai = °' = °- j vj u> x u\ [ - x Yf<j 3 Given the definition of the net Y^ Y i) y ii' — [x,j] Y^ ^ < Y M> = - 9ho u> A, this implies °> 3 3 = fato 3 The population-weighted = social utility g,j ^'"' °- 3 values add to a positive expression Y i,j f'J 9 'J = Y Pi ("' Xl i\ l 3 LO & ~ u Xh ' \- > °' first- That is, transfers which would be worth doing without an IC constraint are restricted, raising the social marginal utilities of consumption, on average, above the value of resources in the hands of the government. Since the IC constraints are on the high more redistribution from the high earners to the low earners IC constraints straints is Given the equal pay constraint, binding, and it is it is skilled types, on average desirable. follows that only one of the the one on the low discount factor type. To IC con- see this consider the difference in consumption utility from different incomes, A [yh,Vu £j. R] = w This difference in consumption utility is increasing in dA[yh ,yi,Sj,R] u 35 The difference in labor disutility does not constraint is [c kj ] - The low discount more tempted [yi, R] the discount factor, u [cij] > 0. depend on the discount binding on the low discount factor type, factor type. therefore - w3 R] [Vh, j it is factor. Thus if the IC not binding on the high discount factor type values earnings in the first period less and is to switch to the less productive job. Second Best with Small Earnings-Dependent Taxes on Savings 4.2 As above, the sign of the welfare impact of introducing a small linear savings tax or subsidy depends on the welfare weights. Given observability of earnings, the small linear tax on savings could be different for high and low earners. tax on savings (collected in the first = is, f ]P fhj (y h - x hj - ) J ^7 = That A A ( 5Z /« ( y ' " x «) ) n on utilities, Y^ fhjVhj u> " Yl fljlll J u the impact on the Lagrangian constraint, the impact welfare impacts of introducing a period) are obtained by differentiating the Lagrangian (with savings taxation included and the tax rates O^r The is ' i x hj] M made up set at zero): (Vh - x hj) - fa ~ x 'j) + W Vi u ' 1 r "l [- [x h i] (y h (w - - r ») , • of three pieces: the impact on the revenue and the impact on the binding IC constraint. 11 - xu ) The FOC for earnings are 53 fhJ9hj + V-iu' = [xhi\ 0, 3 j Multiplying these by the earnings level at the job, dC and substituting, we have j/*, = 53 fhjQhjXhj + u x hl] x hl, ' l-h [ J = 53 fa9U x U ~ E<9r ; Substituting for n t u' [xu] FOC from the ^ we for earnings, — = fhh9hh (xhh - t^ x "] x "' t find > Xhi) and = KOTi The JihQih [xih ) 0. signs follow from the assumption on the net social marginal utilities in savings behavior by types ih and il for i plays no role in signing these expressions. Proposition skill - xu < 1 jobs and g^j that falls At the second < 0,gij on high earners > is 0, best for j h, is I. The optimum, assuming that = differences correlation between skill and discount The Proposition immediately all h,l, then introduction of a welfare improving; savings that falls on low earners One can — and the high follows. skill workers hold high small linear tax on savings and introduction of a small linear subsidy on welfare improving. increase the redistribution from high earners/high savers by taxing savings, but increasing net-of-tax earnings just enough that the high earners/low savers remain indifferent to job change and thus the binding IC constraint is unchanged. One can also increase the redistribution towards the low earners/high savers by subsidizing their savings, but decreasing net-of-tax earnings such that the low earners/low savers remain indifferent so that it does not become more attractive for the high earners/low savers to take the low job. 12 Second Best with Optimal Linear Earnings-Dependent Taxes 4.3 on Savings We have considered the introduction of small savings taxes on high and low earners. Part of the interest in this analysis comes from the possible link to the signs of the optimal taxes. FOC Derivation of the it for the optimal linear savings taxes straightforward; is we show that matches the signs of the small improvements given the additional condition that workers save more One first if 4 the after-tax return to savings are higher. difference in analysis that changes in both the earnings and savings taxes have a is order effect on tax revenues through the behavioral change in savings. In n revenue from a linear savings tax units, the tax discount factor 5j and earnings y equals T l denote optimal savings dependence on the Sj [y,, R(l — A second difference sv u depends on the level of the savings tax. l^\° K M F«J i_ Ti { Forming a Lagrangian, and assuming that at the is no that the relative is marginal increase in the savings tax compared to the of a marginal increase in earnings dr For notational convenience, r,)]. by s^. (Given preference separability, there r,)] effort to achieve gross earnings.) size of the utility loss of a — period on the savings of workers with levied [yi,R(l sd x first That utility gain is, i-ndVi' optimum each worker is assigned to the matching job, we now have C = Y The htfij FOC H for [W. (! ~ + fi t T i) R \ v zil n i]) \ (wi [y h (1 - , rh ) - x Y Ai tt yi ~ z^ ~ R]-v [z h /n h - w ] t [y u (1 TiS v [W> - r ( ) R) i l - T i) R }} + v [zi/n h ]) . earnings are Y Y fhjVhj u ' x hj] \ + htfljU*' [Xij] fru' - [xhi] fliU - [Xu] Y ^ X - Yl Mlj " 2 ( ( 1 Th l ~FT dy = ) °' - Ti- dy 'Consideration of earnings-dependent nonlinear savings taxation would raise the issue of the degree of complexity that is interesting for policy purposes. L3 FOC The Y for savings tax rates are ftJ IhjVhjU + [Xhj] L i ftu' [xta] Y -r^ h 'h •!• J X fhJ s { ^+ ^ 1 Th = o, OTh I 3 SU Denote by = /?/, respectively the high = R(l — n) R(l - r^) and Ri and low skill find that the optimal linear savings tax fhhQhh {Xhh ~ xm) = rh is r^} 0. the after-tax returns to savings for Combining the types. + first order conditions as before, we such that Y X fhj s hj \ - -Q^Shi + ^y!r Rh ( \ 4) and fihQlh (xih The ~ Xll) = T iY X f'J Sl J I ~ ~d^ S" + TR Rl ^ ' | left-hand sides in equations (4) and (5) correspond to the welfare changes of introducing earnings-dependent taxes on the high earners and low earners respectively. Thus, of the terms in brackets if on the right-hand the introduction of a small tax additive, -^- < 1, and so — s tj is > — dRi n u is -p^-Su > is for i = and vice h,l. versa. Since preferences are Hence, a sufficient condition for that savings are increasing in the after-tax return, the second best optimum, assuming that savings are increasing in the after-tax returns, all high skill workers hold high skill jobs, and g hj < the optimal linear savings tax and negative for is positive for the high earners 0,gij > for j with hours chosen by workers. CES They in their Figure derive the 1. h,l, (2008) (2008) consider two-, three- and four-types models mechanism design optimal preferences with varying correlations between discount and marginal taxes shown — the low earners. Mechanism Design Optimum in Tenhunen and Tuomala As noted above, Tenhunen and Tuomala suming sum - Proposition 2 At 4.4 the positive, the optimal linear tax is positive welfare- improving the right-hand side term to be positive ^ii side if For allocations as- skill, with implicit but very high correlation, they find that sav- all ings are implicitly marginally taxed for the high skill worker with low discount factor (type 3), savings are implicitly subsidized for the low 2), and there are no other marginal savings skill worker with high discount factor (type distortions. 1 I With very high correlation, the low 05 —— i t* 1 type 1 1 1 ....... type 2 1 1 1 1 t / / 025 / / Wffffnm>tllM»t«»tltl»l«»tlHllllltM»JH»»l 1 i / •025 0 0: 5 correlation FIGURE 1 Marginal tnx on savings worker with low discount factor (type skill m the welfarisf cnse 1) is implicitly taxed, which also happens in the two type model, which has perfect correlation. The potential relevance of the pattern we find is enhanced by their findings. mechanism design optimal In contrast with our model, the allocation allows distortion of the savings of each type separately. is not too high, on average the savings tax low skill positive for the high skill we levels in main allow different ability levels for the two high earner types. Second, all four types. Third, High Earners assume that the two types with high high skill is skill allow different the analysis extends to three sufficiently more 1 continues to hold. skilled, skill if skill which IC constraint is \r> As long skill as the type with low may be more tempted required. For given skill of type hh, binding holds higher than h M (> n hh ), where the cut-off level n M model above, we the type with low discount the type with high discount factor is skill. than the high However, to switch to the low earner job for which less output this reversal of In the four-types have exactly the same type with high discount factor has higher discount factor, Proposition factor we show how we propositions. workers and jobs, preserving the various assumptions. Different Ability Levels of the , for the types. discount factors for is and negative consider three extensions to highlight the extent of robustness of the First, n hh as the correlation Robustness 4.5 We is As long is when the ability level n M of type hi such that the IC constraint is just binding on both types, {wi [y h , R] - v {zh /h M )} ~ W'i [Vi, R]-v {zi/hhi)} = {wh With is [yh, R]-v (zh /nhh )} - {w h [y t , R]-v (zi/nhh )} v [z/n] convex, the difference in labor disutilities between jobs, {v (zi/n) n^ decreasing in n. Hence, for values of for the n« higher than the IC constraint is — . v (zh/n)}, more stringent high discount saver. In this case, a savings subsidy on the high earners and a savings tax on the low earners are welfare improving. This among Different Discount Factors the opposite of Proposition is the High and earnings and no taxation of savings, a high Low With Savers 1. job-specific worker considering switching to the low job skill chooses optimal savings without needing to match any particular worker holding the low job. Thus, with the is same skill always higher for the high the discount rates among among skill worker the low introducing taxation of savings high earners, the gain from switching to the low job skill among who has lower preference for savings, regardless of We workers. continue to have a welfare gain from high earners as in Proposition 1. Subsidization of savings of low earners will continue to generate a welfare gain as long as the discount factor of the high-skill low-saver of discount factors among holders of the low consumption of the high-skilled low saver on that job if small enough relative to the distribution is skill job. Denoting by taking the low skill job, x^i the first-period the FOC for earnings is: 3 The impact of a savings tax on low earners 7^7 = Yl is f'j9ijXij ~ hu ' [x'hi] xM . 3 Comparing the consumption among low in the earners, this derivative IC constraint with a weighted average of consumptions is savings of low earners in Proposition negative (and the gain from the subsidization of the 1 _ continues to hold) __ and only if xM > xi, where Ej fij9ijXij Yl j With the if fijSij net marginal social values assumption, gy 16 > 0, for j — h, /, x~i is a proper weighted — — average of the Xy. Since the discount rates for the marginal high high to meet this condition, we type skill may well be too consider the tax of the savings of higher earners to be a more robust policy conclusion than the subsidization of the savings of low earners. We are exploring two extensions to the basic model, one with an education choice and one with a continuum of worker types. In both cases, preliminary work suggests the same pattern of greater robustness of the taxation of higher earners than of the subsidization of lower earners. 5 Three Ability Levels, Three Jobs We extend optimum skilled We introduce an intermediate skill level in the model. the assumption that welfare weights and population fractions are such that at the the high skilled are on the most productive job to also have all on the intermediate job. We all the intermediate again consider the case in which agents may be tempted Only two downward constraints are relevant to switch to jobs designed for less skilled people. though. First, as above, for constraint two agents with the same but different discount factors, the IC skill, slack for the type with the higher discount factor is with the lower discount factor. The reason A both [2/1,2/2, 5j, — — dA[ym ,yi,6j,R] — - > - = R] - w3 Wj [yi,R] and binding for the type that, with is = if it is — [y 2 — R] , d^{yh ,y — ,8J- ,R] do l , . > - for i — m, I. ad Second, with v [z/n] convex, we have a similar condition for the difference in the' disutility of labor between jobs. That is, A' with [z h dA'[z h ,zi,n] Thus, for , zi,n] = {-v , = v [z h [z h /n\ two agents with the same discount low-skilled job is /n] zh + - v [z,/n\ , , v [z[/n\ z factor, the L ) 2 jn < 0. IC constraint of switching to the slack for the type with the highest ability if it is satisfied for the type with the intermediate ability switching to the low-skilled job and for the type with highest ability switching to the intermediate job. That is, the local IC constraints imply the global IC constraint. In a similar way 'With heterogeneity in education. If as for the four-types model, in discount factors, people we can who discount the only education determines a worker's factors than low-skilled workers. 17 skill level, set up the Lagrangian future less may for the choose to invest more high-skilled workers have higher discount , . The two constrained maximization problem. Wi wi The impact [y R]-v [z h /n h [y h , m R] , - v [z m /n m relevant ] > w t [y } > w t [y h IC constraints are m , - R] R] - m /nh v [z v [zi/n m ] ] of the introduction of earnings-dependent savings taxes on the Lagrangian equals respectively — = a OT h fhh9hh {xhh - xM > ) 0, DC JmhQmh \%mh ~7\ DC = 77- or This implies that Proposition The - xu ) < < ^i 0. 1 continues to hold for the high earners and the low earners. 1 following Proposition applies for the intermediate earners. Proposition 3 In a model with redistribution three ability levels on savings that linear tax (subsidy) if fihQih (xih %ml) from (to) the falls and three jobs, the introduction of a small on the intermediate earners is welfare improving intermediate earners to (from) general revenues is welfare improving. Proposition 3 implies that there is a single sign change in the response of welfare to taxing savings as a function of earnings. This result generalizes for more than three jobs as well, the welfare weights are non-increasing in The skill. if savings of workers with earnings below a given level are subsidized, the savings of workers with earning above that level are taxed. The result depends on the assumption that types with the same skill are at the same job, which becomes increasingly strained with many jobs. The single sign change of the welfare impact of introducing a savings tax as a function of earnings also holds for the optimal linear earnings-dependent savings taxes [x] = optimal savings tax rate is CRRA preferences, u distributed across jobs, f }] -t^- = 0, jz~i an d 7 fij 1- With logarithmic — f3 for Vz, j. fj for \/i,j and ~ xu) first-period workers if u = T, i = log [x], the s,j = -j^yi and satisfies ^ \fij-~Xu. consumption x io 18 [x] they are uniformly Since for logarithmic preferences the optimal tax on the savings of earners at job — preferences, strictly increasing in the earnings of fih9ih (Xih With < when workers have — j^-yi, we find the following , , expression for the optimal savings tax, - {Si fh A S h ) (r\ ih 7"i EiVi&;\» Since <$/, > 5i, with the welfare weights non-increasing linear savings tax is + l 5 in skill, this implies that the optimal increasing in earnings, dTi >0 7T oyi - Second Best with Uniform Taxes on Savings 5 Proposition 1 what leaves the natural question of the tax rate on savings oc - = dc a Ot dr h oc , ^r- = for both earnings levels. ~ JhhQhh {Xhh . . Xhl) + . ~ Jlh9lh {%ih Xii) Oti In contrast with the earnings-varying tax on savings, the correlation between count factor plays a role here. If there is no desire to redistribute within a job, r hh9hh r Jih9ih Jhh = y^ = ^ ST~^ r y , Thj9hj , Y~^ > Jlh , c = gu, for — - vJhh = Jij9ij ##, , f' h ^ I l-H r h,l, r then -i [x fJ-iU I , = i M \ 1 u F«J • Thus, the welfare impact of a change in the uniform tax on savings equals It is Adding the we have responses to the two separate tax changes, "H do with a Nordic dual income tax where same required to be the is to 9£ ( »T \L,-/m fhh , r n / flh N A n]/ Lj/y / convenient to write this as 9£ _ . „__„ w flh , r „ ! , {x „ _ ^J^^n ' fhhTLjfh] with _ u'\x hl (x hl ] U' [x a ] {Xu 19 - x hh - Xih) ) - \ i j skill and dis- Since Xu > xih, S ,g n _ (_j {-jj^jrO ~ S , 9n 1 j The sign of this expression depends on the distribution of types and the ratio of the weights, Q. That 1h > 12 j fhj Q > is, y/" Hj , 1 is a sufficient condition for a positive correlation between aspects, to imply that introducing a savings tax increases social welfare. 1 , flj Assuming homothetic u Chl \f This expression . { preferences, so that y— = we [x] Thus, the relative risk aversion 7 if between is larger than is factor smaller than (i.e. y/ hf t 1, > if 7 is Proposition 4 with CRRA greater than is no desire // there is -preferences, A uniform 1 then y/" , 0, > 1 and a positive correlation implies that |^ 1 ) when the correlation to redistribute within a job, positive. is one and the correlation between ability small subsidy on savings increases welfare If there is — g,f, gu, for no desire if the if and discount factor the correlation between ability As with the some tax returns to savings and by the savings of type and the after-tax we Sij interest rate. interesting cases. CAR A When h,l, relative is the relative risk aversion g^ — negative. is gu, for 1 = h,l, with if and positive (negative). ij Denote by R T = R(l—r) the after- as a function of after-tax earnings Setting the derivative of the Lagrangian with respect to r - xM ) + fihQih {xih ~ xu) = \J d t } U ''For is find the following condition for the optimal linear tax, fhh9hh (xhh negative. 7 earnings- varying taxes, the sign result for introducing a uniform tax matches that for optimal linear taxation in equal to zero, is — and discount factor and discount factor within a job, to redistribute if i logarithmic preferences, a uniform small tax (subsidy) on savings increases welfare only If negative, |^ is a uniform small tax on savings increases welfare greater than one and the correlation between ability Corollary prefer- This implies the following proposition. 1. risk aversion is smaller than positive. CRRA For the sign of |^ depends on the size of the correlation and the magnitude 1, of the earnings difference between jobs. Conversely, negative becomes f2 find and discount ability the expression for -, equal to one for the log utility function. is ences, u , = £M ^M preferences, §y the correlation is is Xf i:j \ s^ (-/ O ij - ~-Su + w^-Rt dyi 1 -i dRT negative when the correlation between ability and discount factor dc is positive if the absolute risk aversion is sufficiently sma dr positive, ^ 20 is If sum the positive of the terms in brackets Proposition 5 If there is logarithmic preferences or is we have the introduction of a small uniform tax if logarithmic preferences and savings positive, is CRRA welfare improving. This within a job, g,h to redistribute preferences with 7 positive if the correlation between ability < 1, = g,i, for the optimal linear and discount factor is is 7 < preferences with relative risk aversion no desire CRRA is that the optimal uniform tax is the case for 1. i = h,l, with uniform tax on positive. Two Types 6 Using a model with two types of workers, a high-skilled worker with high discount factor and a low-skilled worker with low discount factor, the empirical finding of a positive correlation between skill and savings rates is treated as a perfect correlation. In this model, positive (negative) marginal earnings taxation then there (negative) marginal savings taxation. The corollary is if design optimum has the same property. to realistic diversity in the economy. The source that introducing savings taxation is If The full is is mechanism seem robust of this inference does not With two-dimensional earners with both high and low savings rates. there a gain from introducing positive redistribution goes from the high earner to the low earner. a gain if heterogeneity, there are low a high earner can imitate the savings of a low earner with the same savings propensities, a savings tax on the low earner does not work to discourage the high earner from imitating. Thus to model less-than-perfect correlation, we use the four-types model with high and low earners with both high and low concern for the future. We The proof parallels model. is in to as Diamond 1 report the results for two types here to and (2003). same result for the contrast with the four types mechanism design optimum, which consider the second-best Pareto frontier with the types referred 2. Proposition 6 In sign (nj We that of the mark the — n 2 ), level is welfare a two-types model without taxes on savings the introduction of a small linear tax (subsidy) improving if and only if and with sign{5\ — on savings = at a given earnings earnings at that level are marginally taxed (subsidized). Corollary 2 In a two-types model without taxes on savings and with sign the introduction of a savings tax 62) on the lower earner is (5i — 62) = sign (nj welfare improving if redistribution goes from the higher earner to the lower earner. The proposition combines the properties of the mechanism design optima in the two separate two-types models with heterogeneity in one dimension. 21 When both types have the — n 2 ), same discount but different factor, are marginally taxed or subsidized (Mirrlees, 1971). the earnings of the potentially imitated type abilities, the ability of that type if when both types have the same Similarly, same discount Stiglitz, 1976). lower or higher respectively. is factor, distorting savings does not help separate the Similarly, both types have the same if marginal taxation.' However, when the two types both the marginal taxation subsidization) of savings is but different discount ability, type are marginally taxed or subsidized factors, the savings of the potentially imitated the discount factor for that type lower or higher respectively is both (or subsidization) of earnings both types have the If two types (Atkinson and earnings are not subject to ability, differ in and discount ability factor, and the marginal taxation (or used to separate types. Preferences and IC Constraints 7 Above we used the utility functions u [x] + 8jU [c] — v [z/rij]. This family of has the property that those with higher savings rates (larger values of work to increase for a given amount of additional pay. But that utility functions {u [x] reversed pay. If - + 5jU [c]) — /5j v = [z/rij] u [x] /8j + u — [c] utility functions 5j) are more not the only is which the savings and labor supply decisions can be connected. is if willing way in For example, with the v [z/rij], the relationship those with higher savings rates are less willing to increase work for additional we had assumed this class of functions, then of desirable savings taxes in Proposition saver would imply that it is 1 we would have reversed the pattern having the IC constraint bind for the high - not binding for the low saver, implying, in turn, that there should be a subsidy of savings for high earners and a tax on savings for low earners. More generally, a one-dimensional family of separable utility functions, any pattern between the variation in the interaction in the subutility function of between consumption and labor. This empirical basis for distinguishing which case is more to write utility in the form employed does not, by U [x, c, j] [<p is different. Generally, (but not borrowing against role for discounting it). So modeling on both aspects - in can have consumption and the variation raises the question of identifying relevant. itself, That it shed light on work precedes pay, is its While the formal model has consumption and work simultaneous experience in real time ,z,j], an standard practice empirical reality. in the first period, which precedes spending it continuous time would naturally have a similar saving and willingness to work. But that does not rule out the possibility that the preferences of high and low savers differ in other ways than just 'This can be considered an implication of the Atkinson-Stiglitz theorem, since there everyone has the same subutility function over tax is first not allowed, the two types can be usefully separated by an earnings tax. earnings of the potentially imitated type is is separability period earnings and consumption. Notice that positive if and only 22 if if The marginal tax on that type saves less for the same and a savings the earnings. a discount rate on otherwise identical and utility There are reasons based on casual empiricism for disutility functions (assuming additivity). supporting the appropriateness of using the Modeling savings with rationality and discounting combines formulation employed above. underlying preferences and issues of self-control. As discussed in Banks and Diamond (2008), psychological analyses suggest these are mixed together. We does not apply to working as well as to consuming whether that is working for later consumption or working to influence future work opportunities. That is, working (at with disutility) involves self-control which would be captured human may in the a future payoff. for those with less difficulty in self-control - may show standard see And no reason to think that this a job saving involves self-control. So greater willingness to both work and save, utility function expression. capital investment involves discounting in a similar way In a richer model, to savings decisions and so generate the pattern in the standard model structure, although formal modeling would distinguish between It financial capital accumulations. not easy to find data applying directly to this issue. is answer human and is whether, for a given level of A greater labor supply functions. in circumstances The we want question to those with higher savings rates tend to have skill, complication in looking at data comes from the differences with age, which we address by considering separate age We cells. report a few correlations supportive of a positive correlation among savings propensities, discounting and earnings abilities using the Survey of on time horizon and savings Before turning to the data, we have been levels. Education choices rates, which matter for both them. education skill A and discount model also report is skill some is correlations with of the complications in interpreting the also a complication in interpreting the both ex ante "skill" Presumably, the and discount factor, level of and can not be used affect wage completed education is on average. In addition to affecting ex affect one's discount rate thereafter. rate data across education and discount rate and then in Thus education is a proxy a simple way to distinguish between further difficulty in interpreting the correlations variable while skill is that education is a discrete continuous and varying within education classes. Three-period Model 7.1 We briefly consider a three-period version of the two-period for later taxation. may some effort. reflect increasing in both ex ante skill, We considering. This will bring out data at different ages. There post Consumer Finances, which includes some questions work practice. we 8 set up a three-period model with the same preference structure as the two-period model analyzed, assuming the same discounting for the utility of consumption and the disutility of For discussion of correlations with experimentally measured discount rates, see Chabris et 23 al, 2008. , work and allowing for different skills in the u + [xi] 8u \x 2 ] + 5 2 u two working periods. [c] - - v [zi/m] 5v [z 2 /?i 2 ] Considering the special case with u we have the time [x] = series of log and v [x] = [z/n] k (z/nf +1 / {(3 + 1) consumption and earnings behavior, assuming that hours are a control variable and the marginal tax rate is constant over time (with derivation in the Appendix): X2 = — = 5R %2 -- (5R)- ~2 z 2 /n 2 -- 1/0 ( 1+1//3 n2 \ (5Ry 1/0 1/73 ( n2 \ zi/n-i Thus, those with higher discount factors have more rapidly growing consumption but rapidly growing earnings (for given earnings and work effort The may skills). This suggests that the cross section pattern of be different at different ages. cross-section pattern of time series behavior may be more illuminating than that of single-period behavior since the single-period cross section patterns are dependent on the pattern over time in skills. be concerned about income If we added uncertain effects in rates of return to the model, we would also skills. But these issues, just reporting simple correlations. Data Analysis 7.2 We full both consumption and earnings choices. Consideration of wealth or wealth/earnings ratios are also affected by the time series pattern of we do not explore less first SCF consider the relations among discounting, saving, education and age. We use the panels in 1998, 2001 and 2004, containing information on 13,266 households in total. For savings rates we consider two proxies. worth to earnings regularly or not. 9 for households. The sample is The first proxy The second proxy is is the logarithm of the ratio of net whether people report that they save divided into age-education cells (5-year age groupings from among different statements. We use for this second proxy whether subjects confirm "Save regularly by putting money aside each month." The results are similar (with sign ''Subjects can choose the statement: reversal) with the statement "Don't save - usually spend about as 24 much as income."