Economic advisor and economist
Curriculum Vitae (pdf, January 26, 2016)
The Paper Trail of Knowledge Flows: Evidence from Patent Interferences
We present new evidence of localized knowledge spillovers using a novel database of patent interferences—instances of simultaneous, identical invention by multiple, independent parties.
We present theory and evidence highlighting the role of natural amenities in neighborhood dynamics, suburbanization, and variation across cities in the persistence of the spatial distribution of income. Our model generates three predictions that we confirm using a novel database of consistent-boundary neighborhoods in U.S. metropolitan areas, 1880-2010, and spatial data for natural features such as coastlines and hills. First, persistent natural amenities anchor neighborhoods to high incomes over time. Second, naturally heterogenous cities exhibit persistent spatial distributions of income. Third, downtown neighborhoods in coastal cities were less susceptible to the widespread decentralization of income in the mid-20th century, and increased in income faster after 1980.
In this paper, I study long-run population changes across U.S. metropolitan areas. First, I argue that changes over a long period of time in the geographic distribution of population can be informative about the so- called “resilience” of regions. Using the censuses of population from 1790 to 2010, I find that persistent declines, lasting two decades or more, are somewhat rare among metropolitan areas in U.S. history, though more common recently. Incorporating data on historical factors, I find that metropolitan areas that have experienced extended periods of weak population growth tend to be smaller in population, less industrially diverse, and less educated. These historical correlations inform the construction of a regional resilience index.
Thick Markets and Churning in the Labor Market: Evidence from U.S. Cities
Workers change occupation and industry less often in more densely populated areas, a relationship that had not been previously reported. This reduced-form result is robust to standard demographic controls, as well as to including aggregate measures of human capital and sectoral mix. Analysis of displaced worker surveys shows that this relationship is present in cases of involuntary separation as well. In contrast, we actually find the opposite result (higher rates of occupational and industrial switching) for the subsample of younger workers. These results provide evidence consistent with increasing-returns-to-scale matching in labor markets. Results from a back-of-the-envelope calibration suggest that this mechanism has an important role in raising both wages and returns to experience in denser areas.
Portage and Path Dependence
Many cities in North America formed at obstacles to water navigation, where continued transport required overland hauling or portage. Portage sites attracted commerce and supporting services, and places where the falls provided water power attracted manufacturing during early industrialization. We examine portage sites in the U.S. South, Mid-Atlantic, and Midwest, including those on the fall line, a geomorphological feature in the southeastern United States marking the final rapids on rivers before the ocean. Although their original advantages have long since become obsolete, we document the continuing importance of historical portage sites. We interpret these results as path dependence and contrast explanations based on sunk costs interacting with decreasing versus increasing returns to scale.
Technological Adaptation, Cities, and New Work
Where does adaptation to innovation take place? I present evidence on the role of agglomeration economies in the application of new knowledge to production. All else equal, workers are more likely to be observed in new work in locations initially dense in college graduates and industry variety. This pattern is consistent with economies from the geographic concentration of factors and markets related to technological adaptation. A main contribution is a new measure, based on revisions to occupation classifications, that characterizes cross-sectional differences across cities in technological adaptation. Worker-level results also provide new evidence on the skill bias of recent innovations.
Precision, Bias, and Uncertainty for State Population Forecasts: An Exploratory Analysis of Time Series Models
Many researchers have used time series models to construct population forecasts and prediction intervals at the national level, but few have evaluated the accuracy of their forecasts or the out-of-sample validity of their prediction intervals. Fewer still have developed models for subnational areas. In this study, we develop and evaluate six ARIMA time series models for states in the United States. Using annual population estimates from 1900 to 2000 and a variety of launch years, base periods, and forecast horizons, we construct population forecasts for four states chosen to reflect a range of population size and growth rate characteristics. We compare these forecasts with population counts for the corresponding years and find precision, bias, and the width of prediction intervals to vary by state, launch year, model specification, base period, and forecast horizon. Furthermore, we find that prediction intervals based on some ARIMA models provide relatively accurate forecasts of the distribution of future population counts but prediction intervals based on other models do not. We conclude that there is some basis for optimism regarding the possibility that ARIMA models might be able to produce realistic prediction intervals to accompany population forecasts, but a great deal of work remains to be done before we can draw any firm conclusions.
Gentrification and Transit in Northwest Chicago
LeRoy and Sonstelie (1983) propose that the presence of transit, in combination with declining automobile costs, leads to the gentrification of inner-city, transit-served neighborhoods. This paper attempts to empirically demonstrate whether the existence of transit resulted in phenomena consists with gentrification, utilizing data from northwest Chicago between 1975 and 1991. Using changes in residential property values as an indicator of gentrification, evidence is found that properties closest to transit stations increased in value much more than those farther away, especially in the period 1985-1991. Properties adjacent to transit stations had a 20% higher increase in value compared with those located a half-mile away, supporting the hypothesis that transit access was a spur to gentrification. The data also supports the notion that gentrification has spread like a "wave" over time, moving away from Lake Michigan and downtown Chicago.
We contrast evidence of urban path dependence with efforts to analyze calibrated models of city sizes. Recent evidence of persistent city sizes following the obsolescence of historical advantages suggests that path dependence cannot be understood as the medium-run effect of legacy capital but instead as the long-run effect of equilibrium selection. In contrast, a different, recent literature uses stylized models in which fundamentals uniquely determine city size. We show that a commonly used model is inconsistent with evidence of long run persistence in city sizes and propose several modifications that might allow for multiplicity and thus historical path dependence.
The Puzzling Persistence of Place
In this article, I explore the remarkable persistence of urban development patterns over decades, centuries, or even millennia. Is such extreme persistence desirable? What does it imply about today's "place-making" policies?
The Paper Trail of Knowledge Transfers
Why do firms tend to locate near other firms? Economists suspect that geographic clustering spurs innovation by letting businesses tap a climate rich in informal transfers of knowledge. By tracing links between inventors filing for patents for the same inventions, I review new evidence supporting the idea that proximity offers businesses tangible benefits.
Geography, History, Economies of Density, and the Location of Cities
Economists believe that people choose to live and work at sites that have productive or amenity value such as a river, harbor, or some other natural resource. Another factor that may determine the location of a city is the benefits derived from density itself: agglomeration economies. Although these complementary explanations both have something useful to say about the locations and sizes of cities, they also have important limitations. While natural features seem important, it is difficult to point to one or even several that are valuable enough to explain a very large metropolitan area. And if there are large economies of density, then any location could be the potential site for a city, since density itself provides a reason for further concentration. If you were to replay the settlement of some large expanse of land, perhaps cities in this alternative history would be of different sizes and locations. This “path dependence” or “history dependence” is a potentially important theoretical implication of models featuring economies of density. In this article, I shed light on why cities are located where they are.
Urban Productivity Advantages from Job Search and Matching
Densely populated areas tend to be more productive. Of course, the cost of living and producing in these locations is higher because congestion raises the cost of scarce fixed resources such as land. But despite the higher prices, many people and businesses continue to live and work in these areas. Why? One explanation is that these locations have natural advantages, such as proximity to a river. Another says that this concentration of households and businesses by itself generates productivity advantages in the form of agglomeration economies. In studying these agglomeration economies, economists have pursued two other questions. Do agglomeration economies exist and how big are they? And what are the precise sources of these agglomeration economies? In this article, I describe the evidence for agglomeration economies from job search and matching and then asks whether it may be large enough to offer meaningful explanations for differences in productivity and density.
Data on new occupation titles and codes ("new work") in the Dictionary of Occupational Titles, 1964, 1977, 1991, and the US Census, 1980, 1990, and 2000. Used in "Technological Adaptation, Cities, and New Work" (2011), Review of Economics and Statistics 93 (2): 554-574.
Last updated February 11, 2016
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