外文文献翻译原文及译文
标题：地铁与城市发展外文翻译2019
文献出处：Marco Navarro, Matthew Turner. Journal of Urban Economics, Volume 108, November 2018, Pages 85-106
译文字数：4500 多字
英文
Subways and urban growth: Evidence from earth
Marco Navarro，Matthew Turner
documented翻译Abstract
We  investigate  the  relationship  between  the  extent  of  a  city’s subway network, its population and its spatial configuration. For the 632 largest cities in the world we construct panel data describing population, measures  of centralization calculated  from  lights  at  night  data,  and  the extent  of  each 
of  the  138  subway  systems  in  these  cities.  These  data indicate that large cities are more likely to have subways but that subways have  an  economically  insignificant  effect  on  urban  population  growth. Our data also indicate that subways cause cities to decentralize, although the  effect  is  smaller  than  previously  documented  effects  of  highways on decentralization. For a subset of subway cities we observe panel data describing subway and bus ridership. For those cities we find that a 10% increase in subway extent causes about a 6% increase in subway ridership and has no effect on bus ridership.
Keywords：Subways，Public      transit，Urban      growth，Urban decentralization
1. Introduction
We  investigate  the  relationship  between  the  extent  of  a  city’s subway  network  and  its  population,  transit  ridership  and  spatial
configuration. To accomplish this investigation, for the 632 largest cities in  the  world  we  construct  panel  data  describing  population,  total  light, measures  of centralization calculated  from  lights  at  night  data,  and  the extent of each of the 138 subway systems in these cities. For a subset of these  subway  cities  we  also  assemble  panel  data  describing  bus  and subway ridership.
These  data  suggest  the  following  conclusions.  First,  while  large cities  are  more  likely  to  have  subways,  subways  have  a  precisely estimated near zero effect on urban population growth. Second, subways cause  cities  to  decentralize,  although  this  effect  appears  to  be  small relative to the decentralization caused  by radial highways. Third,  a 10% increase  in  subway  extent  leads  to  about  a  6%  increase  in  subway ridership  and  does  not  affect  bus  ridership.  A  back  of  the  envelope calculation suggests that only a small fraction of ridership increases can be accounted for by decentralized commuters. Together with the fact that little new ridership can be attributed to population growth, this suggests that  most  new  ridership  derives  from  substitution  from  other  modes  of travel towards subways.
Subway  construction  and  expansion  projects  range  from  merely expensive to truly breathtaking. Among the 16 subway systems examined by Baum-Snow and Kahn (2005), construction costs range from about 25 million to 550 million USD2005 per km. On the basis of the mid-point of
this range, 287 million per km, construction costs for the current stock are about 3 trillion dollars. These costs are high enough that subway projects generally  require  large  subsidies.  To  justify  these  subsidies,  proponents often  assert  the  ability  of  a  subway  system  to  encourage  urban growth.1 Our  data  allow  the  first  estimates  of  the  relationship  between subways  and  urban  gro
wth.  That  subways  appear  to  have  almost  zero effect on urban growth suggests that the evaluation of prospective subway projects should rely less on the ability of subways to promote growth and more on the demand for mobility. Our data also allow the first panel data estimates  of  the  impact  of  changes  in  system  extent  on  ridership  and therefore also make an important contribution to such evaluations.
Understanding  the  effect  of  subways  on  cities  is  also  important  to policy makers interested in the process of urbanization in the developing world.  Over  the  coming  decades,  we  expect  an  enormous  migration  of rural  population  towards  major  urban  areas,  and  with  it  demands  for urban  infrastructure  that  exceed  the  ability  of  local  and  national governments to supply it. In order to assess trade-offs between different types  of  infrastructure  in  these  cities,  understanding  the  implications  of each  for  welfare  is  clearly  important.  Since  people  move  to  more attractive places and away from less attractive ones (broadly defined), our investigation of the relationship between subways and population growth will  help  to  inform  these  decisions.  In  particular,  if  the  objective  of
policymakers  is  to  increase  a  city’s  population  or  to  decentralize economic activity, highways seem more promising. On the other hand, in a related companion paper, Gendron-Carrier et al. (2017)
show that if the objective is to reduce pollution, then subways can be effective.
Finally,  an  active  academic  literature  investigates  the  effect  of transportation infrastructure on the growth and configuration of cities. In spite of their prominence in policy debates, subways have so far escaped the attention of this literature. This primarily reflects the relative rarity of subways. Most cities have roads so a single country can provide a large enough sample to analyze the effects of roads on cities. Subways are too rare  for  this.  A  statistical  analysis  of  the  effect  of  subways  on  cities requires data from, at least, several countries. An important contribution of this paper is to assemble data that describe all of the world’s subway networks. In addition,  with few exceptions,  the current  literature  on the effects of infrastructure is static or considers panel data that is too short to investigate the dynamics of infrastructure’s effects on cities. Because our panel  spans  the  60  year  period  from  1950  until  2010,  we  are  able  to investigate such dynamic responses to the provision of subways.
To estimate the causal effects of subways on urban growth and urban form, we must grapple with the fact that subway systems and stations are not constructed at random times and places. This suggests two potential threats  to  causal  identification.  The  first  could  occur  if  subway
expansions  systematically  take  place  at  times  when  a  city’s  population growth  is  slower  (or  fas
ter)  than  average.  For  example,  if  construction crews  leave  the  city  when  new  subway  expansions  are  complete  or  if subway  expansions  tend  to  occur  when  some  constraint  on  a  city’s growth  begins  to  bind.  The  second  results  from  omitted  variables.  For example,  suppose  that  cities  expand  their  bus  networks  in  years  when they  do  not  expand  their  subway  networks  and  that  bus  and  subway networks contribute equally to population growth. Then any regression of population  growth  on  subway  growth  that  omits  a  measure  of  the  bus network  will  be  biased  downward.  Briefly,  we  address  the  problem  of confounding dynamics by showing that the null population growth result is  invariant  to  using  first  differences,  instrumented  first  differences, second  differences  and  dynamic panel  data  models.  The  instrument  we propose  takes  advantage  of  the  fact  that  larger  subway  systems  grow more slowly and this allows us to predict subway growth using long lags of  subway  system  size.  We  address  the  omitted  variables  issue  by showing  that  the  null  effect  of  subways  on  population  is  not  masking heterogenous  effects  by  measures  such  as  congestion,  road  supply,  bus supply, institutional quality, city size, or size of network, among others.
2. Literature
2.1. Subways
With  a  few  exceptions  that  we  describe  below,  the  literature  that

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