Although economists have long been aware of Jensen's inequality, many econometric applications have neglected an important implication of it: the standard practice of interpreting the parameters of log-linearized models estimated by ordinary least squares as elasticities can be highly misleading in the presence of heteroskedasticity. This paper explains why this problem arises and proposes an appropriate estimator. Our criticism to conventional practices and the solution we propose extends to a broad range of economic applications where the equation under study is log-linearized. We develop the argument using one particular illustration, the gravity equation for trade, and apply the proposed technique to provide new estimates of this equation. We find significant differences between estimates obtained with the proposed estimator and those obtained with the traditional method. These discrepancies persist even when the gravity equation takes into account multilateral resistance terms or fixed effects

The Log of Gravity

We develop a Ricardian trade model that incorporates realistic geographic features into general equilibrium It delivers simple structural equations for bilateral trade with parameters relating to absolute advantage, to comparative advantage (promoting trade), and to geographic barriers (resisting it) We estimate the parameters with data on bilateral trade in manufactures, prices, and geography from 19 OECD countries in 1990 We use the model to explore various issues such as the gains from trade, the role of trade in spreading the benefits of new technology, and the effects of tariff reduction

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Technology, Geography, and Trade

We analyze the effect of rising Chinese import competition between 1990 and 2007 on US local labor markets, exploiting cross-market variation in import exposure stemming from initial diffe...

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The China Syndrome: Local Labor Market Effects of Import Competition in the United States

Urban performance currently depends not only on a city's endowment of hard infrastructure (physical capital), but also, and increasingly so, on the availability and quality of knowledge communication and social infrastructure (human and social capital). The latter form of capital is decisive for urban competitiveness. Against this background, the concept of the “smart city” has recently been introduced as a strategic device to encompass modern urban production factors in a common framework and, in particular, to highlight the importance of Information and Communication Technologies (ICTs) in the last 20 years for enhancing the competitive profile of a city. The present paper aims to shed light on the often elusive definition of the concept of the “smart city.” We provide a focused and operational definition of this construct and present consistent evidence on the geography of smart cities in the EU27. Our statistical and graphical analyses exploit in depth, for the first time to our knowledge, the most re...

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Smart cities in Europe

The last few decades have seen a spectacular integration of the global economy through trade. The share of imports (or exports) in GDP for the United States has approximately doubled in the last two decades, and if intra-OECD trade is omitted, the same is true for the OECD countries generally. Trade does remain a seemingly small fraction of U.S. GDP. This is not surprising in view of the fact that large economies trade less with others, and more internally. But the modest share of trade in total national income hides the fact that merchandise trade as a share of merchandise value-added is quite high for the United States and the OECD, and has been growing dramatically. In fact, if one focuses on merchandise trade relative to value-added, the world is much more integrated today than at any time during the past century. The rising integration of world markets has brought with it a disintegration of the production process, in which manufacturing or services activities done abroad are combined with those performed at home. Companies are now finding it profitable to outsource increasing amounts of the production process, a process which can happen either domestically or abroad. This represents a breakdown in the vertically-integrated mode of production—the so-called ‘‘Fordist’’ production, exemplified by the automobile industry—on which American manufacturing was built. A number of prominent researchers have referred to the importance of the idea that production occurs internationally: Bhagwati and Dehejia (1994) call this ‘‘kaleidoscope comparative advantage,’’ as firms shift location quickly; Krugman

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Integration of Trade and Disintegration of Production in the Global Economy

We consider the distribution of economic activity within a country in light of three leading theories—increasing returns, random growth, and locational fundamentals. To do so, we examine the distribution of regional population in Japan from the Stone Age to the modern era. We also consider the Allied bombing of Japanese cities in WWII as a shock to relative city sizes. Our results support a hybrid theory in which locational fundamentals establish the spatial pattern of relative regional densities, but increasing returns help to determine the degree of spatial differentiation. Long-run city size is robust even to large temporary shocks.

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Bones, bombs and break points: The geography of economic activity

How does trade liberalization affect wages? This is the first paper to consider in theory and data how the impact of final and intermediate input tariff cuts on workers' wages varies with the global engagement of their firm. Our model predicts that a fall in output tariffs lowers wages at import-competing firms, but boosts wages at exporting firms. Similarly, a fall in input tariffs raises wages at import-using firms relative to those at firms that only source locally. Using highly detailed Indonesian manufacturing census data for the period 1991 to 2000, we find considerable support for the model's predictions.

Trade, Firms, and Wages: Theory and Evidence

A half-century of empirical work on the factor proportions theory has identified devise simple amendments that bring theory and data into reasonable congruence. Our study considers standard and novel hypotheses regarding the failures of the Heckscher-Ohlin-Vanek formulation and is the first to examine these directly on the technology and absorption data of interest. We show how a few simple and plausible amendments, verified directly by this data, suffice for a striking confirmation of the HOV theory. Countries export the services of abundant factors and in approximately the right magnitude. HOV works.

An Account of Global Factor Trade

http://www.columbia.edu/~drd28/Heckscher_OR.pdf

Intra-industry trade: A Heckscher-Ohlin-Ricardo approach

There are two principal theories of why countries or regions trade: comparative advantage and increasing returns to scale. Yet there is virtually no empirical work that assesses the relative importance of these two theories in accounting for production structure and trade. We use a framework that nests an increasing returns model of economic geography featuring "home market effects" with that of Heckscher-Ohlin. We employ these trade models to account for the structure of regional production in Japan. We find support for the existence of economic geography effects in eight of nineteen manufacturing sectors, including such important ones as transportation equipment, iron and steel, electrical machinery, and chemicals. Moreover, we find that these effects are economically very significant. The latter contrasts with the results of Davis and Weinstein (1996), which found scant economic significance of economic geography for the structure of OECD production. We conclude that while economic geography may explain little about the international structure of production, it is very important for understanding the regional structure of production.

Donald R. Davis

Papers

Bones, bombs and break points: The geography of economic activity

Trade, Firms, and Wages: Theory and Evidence

An Account of Global Factor Trade

Intra-industry trade: A Heckscher-Ohlin-Ricardo approach

Economic geography and regional production structure: an empirical investigation