,
.Book Reviews
Jay \V. Porrestcr, li6ua D,?ranics, with a Foreword by John F. Chliins. The M.I.T.
Prey, Cambridge, Maar., and London, England, 1!%9. 281 pages, Prire Sl’2.W.
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Forrettter’s book on f.~r&unI>p&$
reminds nnc of an early scientific treatise on &emi~q OF Phy&~ Ek-ing under Ihe influencr of what lsard has raIled the “Anglo-Saxon
bii” which is the n&ion that relationships expressibIc through time arc mow fundatn~tttil than those extending across space, the author sets out to develop the “cquatiotw
d motion” of the “urban system.” And hc accomplishes this9 task with unique rigor
and scientific clcg~ancc through the development of a model capable of simulating a
hypothetical city (or “urban area”; front birth to old agr, a life cy& of 2.30 yars nf
internal devebpment, maturity, and sragnation.
‘V;r model de& w<th a fixed land area; starting initially with nearI> empty land, it
generates the 1ifeqcC oii devclopmcnt leading to full land occupancy and equilibrium.
A variation of the model b started with equilibrium initial rondetions in order tti
explore the intpac3 cmfalternative politics on the Mlowing .50 years.
The: intcrna1 structure of the model consists of the identification of thrcr aulaysterm.
timely industry, ho&ng, and people. The three subsystems interart thnjugh nine
&te (or l~cl) and twenty-two raft variables. The interrelationship among the vnriahks
take the form of initial paramrtcrs, rate equations, level rquations, and auxiliary quations. The rate equations art “the statements of system policy,” in that the) c.!
the discnrpncy between the goal and the ob~rved condition and a’taothe action
will re4t Corn the discrepancy. The level equations compute a npbv value by taking
the oM value and adding the change during the preceding time interval. The auxiliary
equalions trarulwte information about Irwts of variables through various multiplirrJ
to pnduce changes in rates within the system. So rate can dire< tly a&t any other
rate and no Ievcl”direc-tly atferts any other Icvrl. One level ran affect another only
through an intervening rate. It is in setting up the interrelationships for a dynamic
n&t4 ofa complex system that Prof&sor Forrester exhibits, as in his previous work,* hi
great talent and skill. MC succet& in developing an operational dynamic model of
the urban system, which, although it might not yrt be a good representation of the
real world, helps the reader understand some fundamental functional relationship of
the system.
The first subsy~tetn in the model is the industrial sutqsystem which contains thret levels
and Gmr rates representing business activity. InitiaUy the& is only new industp in the
city, which through the natural process of a.ging iu gradually trannforrmd to the categotics flcvek) of mature businlrre and then to declining industry. The flow from one
hosinvxs category to the next depends, in Forrester’s words, “not only on time but on
the condition of the entire urban system.”
The mnd
suhtystcm, cont:&ing three Ltveh and six rata, represents the conatrtx$ot~, aging, and demolition of housing. The third subsystem, with three levc&s
and tweke rates, nptwcttts the yoptdation. Fach level of the hot&g and$r poptdadon suhrtijtems corresponds to one of the three kinds of People in the city: “managerial-
a* *+lal~or” (skilled labor fully participating in the urban ccrmotn~~, ;u#l
~~und~~pk~ed”
(in&ding uncmpbycd and urtskibd work-).
1%~ three kvek ~8
Wng
arr : &mbn
housing, worker housing, and uncicrcmpkyxi hnrrrittg. Premium
I poputatinn, and uith
howiIt#J is initiony conttructd fos the mstnagcrial-pr
the pmqgc of time ckteriorrta into the worker-housing category. Worker housiw ran
ah he dircdy constructed, and this category ~gcs and dcclincs into the und=mpi+‘ed
houalng cat-.
it is d interest to mtc that the process d grnwth to swati<%
t&cctaj in the tit!: life c$c, is structuralt~ built into twn nf t;hc three irutwrptcm9 of
the nm&l. In the indu&rial subgrtcm rtcw entcrpriscs bectrme mature hu&Wss NId
then declining industry; similarly in the housing subsystem premium hot&# bccomfl
worker busing and them underemployed housing.
The internal city system, with its three sulx++stem is cmbeddcd in an external
cnvirunmcnt which far the city rcprcxnts a sink-sourec of infinite rapacity. Dcpcndirrq
on the attractivcne~ of the particular urban area relative tn the envirunmcnt, pc4bple
will flaw in or uut ux’thc city. ‘1%~eanccpt ofnttractive~
together with the dclincatbn
of the uirbaln system geographic hounda~ are of fttndamcntal importance l&r tl~
p&y implicrtb
nf the m&cl.
1L?nfbrtunateiy, the boundw
concept ranaim aorndkat aU’Ibi@MJ~
hxot~w
Pl*;f-r
Fatrz~cr does not fist the relevant criteria for boundary delineation. Hrr onl<
suggests $hat one &tx~M “rhoaw a system bounrhty chat defines the cunccpts that
interact to produ~c :hc hehrviour of intcrcst.” At another point hc states that “the ares
is bat t&u&t of BPa section OTane ofour older cities, not as the cntirc arca within tb
pditical t)olmdar):.* It would appear that daily commuting across the rptcm houndar,
will not itdhtcnce the m&cl results. This ofeous3c is open co 9&a
qucbn,
even it
the &xi lcvcl, o.n account of the well known central city--?&u&an
prehkms.
At the global kvci the Fottwter boundary is za&jcct to rncxc serious misintcrprcta
tions. I&u out&de ~nvironmcnt is impiieitly taken a0 a point of r&xcnc+, aincc flow
fmm-and #to the outside are contr&cd only by the lcvcls within the syltcm bmusdar~For CxatlIpk~ a shortage of “underemphr~cd hot&$” makes the city Isa attrartivc tcs
low inc0mc IpGopk, the result being that fCwcr come and man: kavc; the qucbn,
ho~cvcr, -ins
as to where do they go? The assumption
a rcvcnxd trend ofmigratioa from :eic,: A to city B or to rural iifc is vi-~ qucstiarrilblr cvcn under the m*st
advcnc cnnditiosrs. Furthcnnorc, the eurai-urban split is not appticabk any more in
%n itWXta$in& urltanizcd w&d, requiring @obal instcbd of locaiil.cd salulion to
pr&cms, ,Sn other words, what happens to the cities cannot bc scparatczd fpMn the
rauxamdi~~ envirormcnt, and urban poliq planning should take the whole nation
into accou$tt.
.
gH.iJ6-t
of
tint fi-om which people come. The expenditure of taxes is here used as an indicator
&publie sewices, schools, wcifare. and other publir-supported
actiGties. \Vhen ‘I’K:R
ip qttd to I, the PEM is also equal to 1 indicztting that the tax per capita in the area
i the ~amc as that outside; hence there is no incentive to move from the nutsidr into
,j the urkn area. It is in the identification and quantification of such mraaures by means
nf t&k functions that Forrester’s contribuGon to the rmrrcyence of an urban system
s&me
lick. which is esJcntiallp_ what Doxiadis calls Ekirtics.:! Althouyh some of rhe
curves ~nployed
in the exemplary model runs might not be accurate representations
of real-lift situations, they are as important for the emeryrnce ofa rigorous and meaningfurldiscipline for city planning as E~;ic’s law I’& the ideal gases was for chemistry more
than a century ago. There is not yet enough empirical evidenre to substantiate the
raw
and the shapes of the assumed functions; however, this approarh might pay ofl
by gettiny around Ihe inGtive
and phenomenoio+al
mod& used w far for simtrlating the impact of alternative urban policies.
In my view the major shortcoming of Forrester’s work is that he never explicates
the criteria used in evaluating
the pcrformanre of the hypothetic;11 city. The unique
characteristic of the urban system is that it is the type of system where me is dealing
with mdtiplr &jr&-m,
multidiracraional
factors and viewpoints. ‘The .set of viewpoints
from which a particular urban planning prcyram is examined is of basic importance.
lo improve the quality of I&= fi,r all group2
of human wttlement dwellers. whether they live in thr country or in tier rit\.
3-b ultintalc
&&tive,ofCOLIIYJC,
slwdrfbe
ALEKANLWR .v. f:nR6sr.+w
-mp
0 1:. A. i)r*ria&u, MiWr:
&oup. L.mdm, i!m+..
In I~ifraMru~60 f/rr
I~
51ICW.Iej ~~WR~R~Sellkml~ &Whinaw
Puhlmhim
1968, ‘371)pages, $7.50.
.._-.._~__--_
For the last few yrrrj the name Yehezkel l>ror has been aswciated with articles am
RAND C&Porcrtion reports on the subject of public policymaking.
In this bm3k Ih
Dror’s studies and conclusions are presented systematicali)-.
His concern is not witl
specific policies and rttcir content:btit
with the ways in which policies arc made am
the question of whether they are made as well as they ran or should be.
The intended audience for thi> book inrhldes “students and tearhen of potitica
science and of the social sciences in general. policy practitioners, such as plannen
govcmmcnt
oIMalr, and contemplative
politicians, and other persons interested il
policymaking
and public affairs. ” The objectives the author hopes to achieve for thi
audicncE are “{I) to advance the study of public policymaking
as a m;?jor topic a
the social sciences and of human thought in general. and (2) to contribute to th
To a large extent, the author has surreeded il
improvement of public poiicymaking.”
writing a bouk which will bc found readable by this diverse audience. So studmt c
the social sciences will bc “tuned
ofl” by the feeling that the topic is treated in
ruperficial manner or that the book is too insubstantial. Similarly, no practiciw poIii
maker will be driven away by technical jargon or by dry presentation. While makin
no ~wm~tx&scs
with inteIlectual rigor, Dr. Dror presents his atyumcntr in such
way that they can be fallowed easily even by those not accustomed to reading th
sock4 sckncc iitcraturc. Whether the ideas pmknted will be atreprcd quaUp
by a
mttmbrm of this audience, ~CSWCWT, is another matter.
k-wem6iqqI
lkmk-
429
(1970!, +274J