Danny Quah

Galton's Fallacy and Tests of the Convergence Hypothesis

Recent tests for the convergence hypothesis derive from regressing average growth rates on initial levels: a negative initial coefficient is interpreted as convergence. These tests turn out to be plagued by Galtons classical fallacy of regression towards the mean. Using a dynamic version of Galtons fallacy, I establish that coefficients of arbitrary signs in such regressions are consistent with an unchanging cross-section distribution of incomes. Alternative, more direct empirics used here show a tendency for divergence, rather than convergence, of cross-country incomes.

Empirical cross-section dynamics in economic growth

Traditional empirical strategies for studying convergence - more generally, the dynamics and determinants of economic growth, can be misleading if important, underlying permanent or growth components are stochastically time-varying. This paper documents the degree to which this instability characterises the data, and then offers an alternative empirical framework. This alternative, directly modelling the dynamics of the evolving cross-section distributions, applied to cross-country income data yields some interesting insights: economies across the world seem to be converging to a distribution where many remain wealthy, and many remain poor. Those economies able to make the transition from low to high income levels are primarily small and sparsely populated; middle-income ones, by contrast, are a vanishing class.

Empirics for Growth and Distribution: Stratification, Polarization, and Convergence Clubs

This paper studies cross-country patterns of economicgrowth from the viewpoint of income distribution dynamics. Sucha perspective raises new empirical and theoretical issues ingrowth analysis: the profound empirical regularity is an “emergingtwin peaks” in the cross-sectional distribution, not simplepatterns of convergence or divergence. The theoretical problemsraised concern interaction patterns among subgroups of economies,not only problems of a single economys accumulating factor inputsand technology for growth.

Twin Peaks: Growth and Convergence in Models of Distribution Dynamics

Convergence concerns poor economies catching up with rich ones. At is- sue is what happens to the cross sectional distribution of economies, not whether a single economy tends towards its own steady state. It is the latter, however, that has preoccupied the traditional approach to con- vergence analysis. This paper describes an alternative body of research that overcomes this shortcoming in the traditional approach. The new findings on persistence and stratification; on the formation of conver- gence clubs; and on the distribution polarizing into twin peaks of rich and poor|suggest the relevance of a class of theoretical ideas, dierent from those surrounding the production-function accounting traditionally favored.

Regional Convergence Clusters Across Europe

Per capita incomes across European regions are not equal and do not stay constant; regional income distributions fluctuate over time. Such a process could have many possible limiting outcomes: complete equality (convergence), stratification, and continually increasing inequality are but three distinct possibilities. This paper asks if nation-state, macro factors and physical-geography spillover effects help explain the observed distribution dynamics across European regions. Geographical factors are found to matter more than national ones; but both are important for explaining inequality dynamics.

Convergence empirics across economies with (some) capital mobility

This paper uses a model of growth and imperfect capital mobility across multiple economies to characterize the dynamics of (cross-country) income distributions. This allows convenient study of the convergence hypothesis, and reveals, where appropriate, polarization and clumping within subgroups. The data show little cross-country convergence; instead, the important features are persistence, immobility, and polarization, exemplified by “convergence club” or “twin peaks” dynamics.

Exploiting Cross Section Variation for Unit Root Inference in Dynamic Data

This paper considers unit root regressions in data having simultaneously extensive cross section and time-eries variation. The standard least squares estimators in such data structures turn out to have an asymptotic distribution that is neither Dickey-Fuller, nor normal and asymptotically unbiased. Instead, the estimator turns out to be consistent and asymptotically normal, but has a nonvanishing bias in its asymptotic distribution.

The relative importance of permanent and transitory components : identification and some theoretical bounds

Much macroeconometric discussion has recently emphasized the economic significance of the size of the permanent component in GNP. Consequently, a large literature has developed that tries to estimate this magnitude measured, essentially, as the spectral density of increments in GNP at frequency zero. This paper shows that unless the permanent component is a random walk this attention has been misplaced: in general, that quantity does not identify the magnitude of the permanent component. Further, by developing bounds on reasonable measures of this magnitude, the paper shows that a random walk specification is biased towards establishing the permanent component as important.

Spatial Agglomeration Dynamics

This Paper develops a model of economic growth and activity locating endogenously on a 3-dimensional featureless global geography. The same economic forces influence simultaneously growth, convergence, and spatial agglomeration and clustering. Economic activity is not concentrated on discrete isolated points but instead a dynamically-fluctuating, smooth spatial distribution. Spatial inequality is a Cass-Koopmans saddlepath, and the global distribution of economic activity converges towards egalitarian growth. Equality is stable but spatial inequality is needed to attain it.

Searching for prosperity a comment

Abstract Kremer, Onatski, and Stock (KOS) criticize twin peaks dynamics in the evolution of cross-country income dynamics. They suggest instead convergence to a single peak at high incomes, with a prolonged transition when polarization and inequality increase. This article makes three points. First, the data are as consistent with a twin peaks characterization as they are for KOSs preferred description—in KOSs own analysis as well as across other studies. Second, the substantive economic message is identical in both twin peaks and KOS views: the global poor are substantial and will continue so—whether for centuries or for infinity is nit-picking. Finally, getting the empirics right matters greatly for theories of economic growth.