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The Economics of Urban Density

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  • Puga, Diego
  • Duranton, Gilles

Abstract

Urban density boosts productivity and innovation, improves access to goods and services, reduces typical travel distances, encourages energy-efficient construction and transport, and facilitates sharing scarce amenities. However, density is also synonymous with crowding, makes living and moving in cities more costly, and concentrates exposure to pollution and disease. We explore the appropriate measurement of density and describe how it is both a cause and a consequence of the evolution of cities. We then discuss whether and how policy should target density and why the trade-off between its pros and cons is unhappily resolved by market and political forces.

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  • Puga, Diego & Duranton, Gilles, 2020. "The Economics of Urban Density," CEPR Discussion Papers 14768, C.E.P.R. Discussion Papers.
  • Handle: RePEc:cpr:ceprdp:14768
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    1. Stephen J. Redding & Esteban Rossi-Hansberg, 2017. "Quantitative Spatial Economics," Annual Review of Economics, Annual Reviews, vol. 9(1), pages 21-58, September.
    2. Büchel, Konstantin & Ehrlich, Maximilian v., 2020. "Cities and the structure of social interactions: Evidence from mobile phone data," Journal of Urban Economics, Elsevier, vol. 119(C).
    3. Pierre‐Philippe Combes & Gilles Duranton & Laurent Gobillon & Diego Puga & Sébastien Roux, 2012. "The Productivity Advantages of Large Cities: Distinguishing Agglomeration From Firm Selection," Econometrica, Econometric Society, vol. 80(6), pages 2543-2594, November.
    4. Carozzi, Felipe & Roth, Sefi, 2019. "Dirty density: air quality and the density of American cities," LSE Research Online Documents on Economics 103393, London School of Economics and Political Science, LSE Library.
    5. Charlot, Sylvie & Duranton, Gilles, 2004. "Communication externalities in cities," Journal of Urban Economics, Elsevier, vol. 56(3), pages 581-613, November.
    6. Berry, Christopher R. & Glaeser, Edward L., 2005. "Divergence of Human Capital Levels across Cities," Working Paper Series rwp05-057, Harvard University, John F. Kennedy School of Government.
    7. Glaeser, Edward L. & Kahn, Matthew E., 2010. "The greenness of cities: Carbon dioxide emissions and urban development," Journal of Urban Economics, Elsevier, vol. 67(3), pages 404-418, May.
    8. Pierre-Philippe Combes & Gilles Duranton & Laurent Gobillon, 2019. "The Costs of Agglomeration: House and Land Prices in French Cities," The Review of Economic Studies, Review of Economic Studies Ltd, vol. 86(4), pages 1556-1589.
    9. Gilles Duranton & Diego Puga, 2023. "Urban Growth and Its Aggregate Implications," Econometrica, Econometric Society, vol. 91(6), pages 2219-2259, November.
    10. Gabriel M. Ahlfeldt & Stephen J. Redding & Daniel M. Sturm & Nikolaus Wolf, 2015. "The Economics of Density: Evidence From the Berlin Wall," Econometrica, Econometric Society, vol. 83, pages 2127-2189, November.
    11. Klaus Desmet & Esteban Rossi-Hansberg, 2013. "Urban Accounting and Welfare," American Economic Review, American Economic Association, vol. 103(6), pages 2296-2327, October.
    12. Ahlfeldt, Gabriel M. & Pietrostefani, Elisabetta, 2019. "The economic effects of density: A synthesis," Journal of Urban Economics, Elsevier, vol. 111(C), pages 93-107.
    13. Combes, Pierre-Philippe & Gobillon, Laurent, 2015. "The Empirics of Agglomeration Economies," Handbook of Regional and Urban Economics, in: Gilles Duranton & J. V. Henderson & William C. Strange (ed.), Handbook of Regional and Urban Economics, edition 1, volume 5, chapter 0, pages 247-348, Elsevier.
    14. Chang-Tai Hsieh & Enrico Moretti, 2019. "Housing Constraints and Spatial Misallocation," American Economic Journal: Macroeconomics, American Economic Association, vol. 11(2), pages 1-39, April.
    15. Sylvie Charlot & Gilles Duranton, 2006. "Cities and Workplace Communication: Some Quantitative French Evidence," Urban Studies, Urban Studies Journal Limited, vol. 43(8), pages 1365-1394, July.
    16. Henderson, J V, 1974. "The Sizes and Types of Cities," American Economic Review, American Economic Association, vol. 64(4), pages 640-656, September.
    17. Wolfgang Dauth & Sebastian Findeisen & Enrico Moretti & Jens Suedekum, 2022. "Matching in Cities," Journal of the European Economic Association, European Economic Association, vol. 20(4), pages 1478-1521.
    18. Berliant, Marcus & Reed III, Robert R. & Wang, Ping, 2006. "Knowledge exchange, matching, and agglomeration," Journal of Urban Economics, Elsevier, vol. 60(1), pages 69-95, July.
    19. Enrico Moretti, 2013. "Real Wage Inequality," American Economic Journal: Applied Economics, American Economic Association, vol. 5(1), pages 65-103, January.
    20. Enrico Moretti, 2019. "The Effect of High-Tech Clusters on the Productivity of Top Inventors," NBER Working Papers 26270, National Bureau of Economic Research, Inc.
    21. Roback, Jennifer, 1982. "Wages, Rents, and the Quality of Life," Journal of Political Economy, University of Chicago Press, vol. 90(6), pages 1257-1278, December.
    22. Moretti, Enrico, 2004. "Estimating the social return to higher education: evidence from longitudinal and repeated cross-sectional data," Journal of Econometrics, Elsevier, vol. 121(1-2), pages 175-212.
    23. Rebecca Diamond, 2016. "The Determinants and Welfare Implications of US Workers' Diverging Location Choices by Skill: 1980-2000," American Economic Review, American Economic Association, vol. 106(3), pages 479-524, March.
    24. O. Ashenfelter & D. Card (ed.), 2011. "Handbook of Labor Economics," Handbook of Labor Economics, Elsevier, edition 1, volume 4, number 4.
    25. Moretti, Enrico, 2011. "Local Labor Markets," Handbook of Labor Economics, in: O. Ashenfelter & D. Card (ed.), Handbook of Labor Economics, edition 1, volume 4, chapter 14, pages 1237-1313, Elsevier.
    26. Pierre-Philippe Combes & Gilles Duranton & Laurent Gobillon & Sébastien Roux, 2010. "Estimating Agglomeration Economies with History, Geology, and Worker Effects," NBER Chapters, in: Agglomeration Economics, pages 15-66, National Bureau of Economic Research, Inc.
    27. Cecile Gaubert, 2018. "Firm Sorting and Agglomeration," NBER Working Papers 24478, National Bureau of Economic Research, Inc.
    28. Duranton, Gilles & Puga, Diego, 2004. "Micro-foundations of urban agglomeration economies," Handbook of Regional and Urban Economics, in: J. V. Henderson & J. F. Thisse (ed.), Handbook of Regional and Urban Economics, edition 1, volume 4, chapter 48, pages 2063-2117, Elsevier.
    29. O. Ashenfelter & D. Card (ed.), 2011. "Handbook of Labor Economics," Handbook of Labor Economics, Elsevier, edition 1, volume 4, number 5.
    30. Alan Manning & Barbara Petrongolo, 2017. "How Local Are Labor Markets? Evidence from a Spatial Job Search Model," American Economic Review, American Economic Association, vol. 107(10), pages 2877-2907, October.
    31. Adam B. Jaffe & Manuel Trajtenberg & Rebecca Henderson, 1993. "Geographic Localization of Knowledge Spillovers as Evidenced by Patent Citations," The Quarterly Journal of Economics, President and Fellows of Harvard College, vol. 108(3), pages 577-598.
    32. Jorge De La Roca & Diego Puga, 2017. "Learning by Working in Big Cities," The Review of Economic Studies, Review of Economic Studies Ltd, vol. 84(1), pages 106-142.
    33. Fujita,Masahisa & Thisse,Jacques-François, 2013. "Economics of Agglomeration," Cambridge Books, Cambridge University Press, number 9781107001411.
    34. Henderson, Vernon & Mitra, Arindam, 1996. "The new urban landscape: Developers and edge cities," Regional Science and Urban Economics, Elsevier, vol. 26(6), pages 613-643, December.
    35. Pierre-Philippe Combes & Gilles Duranton & Laurent Gobillon, 2011. "The identification of agglomeration economies," Journal of Economic Geography, Oxford University Press, vol. 11(2), pages 253-266, March.
    36. Nathaniel Baum-Snow & Ronni Pavan, 2012. "Understanding the City Size Wage Gap," The Review of Economic Studies, Review of Economic Studies Ltd, vol. 79(1), pages 88-127.
    37. Fran?ois Ortalo-Magn? & Andrea Prat, 2014. "On the Political Economy of Urban Growth: Homeownership versus Affordability," American Economic Journal: Microeconomics, American Economic Association, vol. 6(1), pages 154-181, February.
    38. repec:zbw:bofrdp:2015_027 is not listed on IDEAS
    39. Venables, Anthony & Duranton, Gilles, 2018. "Place-Based Policies for Development," CEPR Discussion Papers 12889, C.E.P.R. Discussion Papers.
    40. Rosenthal, Stuart S. & Strange, William C., 2001. "The Determinants of Agglomeration," Journal of Urban Economics, Elsevier, vol. 50(2), pages 191-229, September.
    41. Hilber, Christian A.L. & Robert-Nicoud, Frédéric, 2013. "On the origins of land use regulations: Theory and evidence from US metro areas," Journal of Urban Economics, Elsevier, vol. 75(C), pages 29-43.
    42. Carlino, Gerald & Kerr, William R., 2015. "Agglomeration and Innovation," Handbook of Regional and Urban Economics, in: Gilles Duranton & J. V. Henderson & William C. Strange (ed.), Handbook of Regional and Urban Economics, edition 1, volume 5, chapter 0, pages 349-404, Elsevier.
    43. Michael Greenstone & Richard Hornbeck & Enrico Moretti, 2010. "Identifying Agglomeration Spillovers: Evidence from Winners and Losers of Large Plant Openings," Journal of Political Economy, University of Chicago Press, vol. 118(3), pages 536-598, June.
    44. Pierre-Philippe Combes & Gilles Duranton & Laurent Gobillon, 2012. "The Cost of Agglomeration: Land Prices in Cities," Working Papers hal-03461075, HAL.
    45. Audretsch, David B & Feldman, Maryann P, 1996. "R&D Spillovers and the Geography of Innovation and Production," American Economic Review, American Economic Association, vol. 86(3), pages 630-640, June.
    46. Carlino, Gerald A. & Chatterjee, Satyajit & Hunt, Robert M., 2007. "Urban density and the rate of invention," Journal of Urban Economics, Elsevier, vol. 61(3), pages 389-419, May.
    47. Ciccone, Antonio & Hall, Robert E, 1996. "Productivity and the Density of Economic Activity," American Economic Review, American Economic Association, vol. 86(1), pages 54-70, March.
    48. Felipe Carozzi & Sefi Roth, 2019. "Dirty density: air quality and the density of American cities," CEP Discussion Papers dp1635, Centre for Economic Performance, LSE.
    49. repec:zbw:bofrdp:urn:nbn:fi:bof-201512111472 is not listed on IDEAS
    50. Gilles Duranton & Diego Puga, 2020. "The Economics of Urban Density," Journal of Economic Perspectives, American Economic Association, vol. 34(3), pages 3-26, Summer.
    51. Henderson, J. Vernon, 2003. "Marshall's scale economies," Journal of Urban Economics, Elsevier, vol. 53(1), pages 1-28, January.
    52. Leo Sveikauskas, 1975. "The Productivity of Cities," The Quarterly Journal of Economics, President and Fellows of Harvard College, vol. 89(3), pages 393-413.
    53. Ioana Marinescu & Roland Rathelot, 2018. "Mismatch Unemployment and the Geography of Job Search," American Economic Journal: Macroeconomics, American Economic Association, vol. 10(3), pages 42-70, July.
    54. Gaubert, Cécile, 2018. "Firm Sorting and Agglomeration," CEPR Discussion Papers 12835, C.E.P.R. Discussion Papers.
    55. Gilles Duranton & J. V. Henderson & William C. Strange (ed.), 2015. "Handbook of Regional and Urban Economics," Handbook of Regional and Urban Economics, Elsevier, edition 1, volume 5, number 5.
    56. Gabriel M. Ahlfeldt & Daniel P. McMillen, 2018. "Tall Buildings and Land Values: Height and Construction Cost Elasticities in Chicago, 1870–2010," The Review of Economics and Statistics, MIT Press, vol. 100(5), pages 861-875, December.
    57. Glaeser, Edward L & Mare, David C, 2001. "Cities and Skills," Journal of Labor Economics, University of Chicago Press, vol. 19(2), pages 316-342, April.
    58. Dave Donaldson & Adam Storeygard, 2016. "The View from Above: Applications of Satellite Data in Economics," Journal of Economic Perspectives, American Economic Association, vol. 30(4), pages 171-198, Fall.
    59. Andrew B. Bernard & Andreas Moxnes & Yukiko U. Saito, 2019. "Production Networks, Geography, and Firm Performance," Journal of Political Economy, University of Chicago Press, vol. 127(2), pages 639-688.
    60. Charles M. Tiebout, 1956. "A Pure Theory of Local Expenditures," Journal of Political Economy, University of Chicago Press, vol. 64(5), pages 416-416.
    61. Gabriel Ahlfeldt & Daniel McMillen, 2017. "Tall Building and Land Values: Height and Construction Cost Elasticities in Chicago, 1870 - 2010," CESifo Working Paper Series 6730, CESifo.
    62. Diego Puga, 2010. "The Magnitude And Causes Of Agglomeration Economies," Journal of Regional Science, Wiley Blackwell, vol. 50(1), pages 203-219, February.
    63. Chun-Chung Au & J. Vernon Henderson, 2006. "Are Chinese Cities Too Small?," The Review of Economic Studies, Review of Economic Studies Ltd, vol. 73(3), pages 549-576.
    64. Combes, Pierre-Philippe & Duranton, Gilles & Gobillon, Laurent, 2008. "Spatial wage disparities: Sorting matters!," Journal of Urban Economics, Elsevier, vol. 63(2), pages 723-742, March.
    65. repec:hal:pseose:hal-00812695 is not listed on IDEAS
    66. Rosenthal, Stuart S. & Strange, William C., 2008. "The attenuation of human capital spillovers," Journal of Urban Economics, Elsevier, vol. 64(2), pages 373-389, September.
    67. Koster, Hans R.A. & Pasidis, Ilias & van Ommeren, Jos, 2019. "Shopping externalities and retail concentration: Evidence from dutch shopping streets," Journal of Urban Economics, Elsevier, vol. 114(C).
    68. Glenn Ellison & Edward L. Glaeser & William R. Kerr, 2010. "What Causes Industry Agglomeration? Evidence from Coagglomeration Patterns," American Economic Review, American Economic Association, vol. 100(3), pages 1195-1213, June.
    69. Donald R. Davis & Jonathan I. Dingel & Joan Monras & Eduardo Morales, 2019. "How Segregated Is Urban Consumption?," Journal of Political Economy, University of Chicago Press, vol. 127(4), pages 1684-1738.
    70. Daniel J. Graham, 2007. "Agglomeration, Productivity and Transport Investment," Journal of Transport Economics and Policy, University of Bath, vol. 41(3), pages 317-343, September.
    71. Melo, Patricia C. & Graham, Daniel J. & Noland, Robert B., 2009. "A meta-analysis of estimates of urban agglomeration economies," Regional Science and Urban Economics, Elsevier, vol. 39(3), pages 332-342, May.
    72. Liu, Crocker H. & Rosenthal, Stuart S. & Strange, William C., 2018. "The vertical city: Rent gradients, spatial structure, and agglomeration economies," Journal of Urban Economics, Elsevier, vol. 106(C), pages 101-122.
    73. Christopher R. Berry & Edward L. Glaeser, 2005. "The divergence of human capital levels across cities," Papers in Regional Science, Wiley Blackwell, vol. 84(3), pages 407-444, August.
    74. Cecile Gaubert, 2018. "Firm Sorting and Agglomeration," American Economic Review, American Economic Association, vol. 108(11), pages 3117-3153, November.
    75. Christopher R. Berry & Edward L. Glaeser, 2005. "The Divergence of Human Capital Levels across Cities," Harvard Institute of Economic Research Working Papers 2091, Harvard - Institute of Economic Research.
    76. Edward L. Glaeser & Bruce Sacerdote, 1999. "Why Is There More Crime in Cities?," Journal of Political Economy, University of Chicago Press, vol. 107(S6), pages 225-258, December.
    77. Jessie Handbury & David E. Weinstein, 2015. "Goods Prices and Availability in Cities," The Review of Economic Studies, Review of Economic Studies Ltd, vol. 82(1), pages 258-296.
    78. Mariaflavia Harari, 2020. "Cities in Bad Shape: Urban Geometry in India," American Economic Review, American Economic Association, vol. 110(8), pages 2377-2421, August.
    79. Christopher R. Berry & Edward L. Glaeser, 2005. "The Divergence of Human Capital Levels Across Cities," NBER Working Papers 11617, National Bureau of Economic Research, Inc.
    80. Small, Kenneth A., 2012. "Valuation of travel time," Economics of Transportation, Elsevier, vol. 1(1), pages 2-14.
    81. Duranton, Gilles & Turner, Matthew A., 2018. "Urban form and driving: Evidence from US cities," Journal of Urban Economics, Elsevier, vol. 108(C), pages 170-191.
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    More about this item

    Keywords

    Density; Agglomeration; Urban costs;
    All these keywords.

    JEL classification:

    • R12 - Urban, Rural, Regional, Real Estate, and Transportation Economics - - General Regional Economics - - - Size and Spatial Distributions of Regional Economic Activity; Interregional Trade (economic geography)
    • R31 - Urban, Rural, Regional, Real Estate, and Transportation Economics - - Real Estate Markets, Spatial Production Analysis, and Firm Location - - - Housing Supply and Markets
    • R32 - Urban, Rural, Regional, Real Estate, and Transportation Economics - - Real Estate Markets, Spatial Production Analysis, and Firm Location - - - Other Spatial Production and Pricing Analysis

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