This paper by Danny T. Quah, published in February 1996, critically reviews traditional and recent approaches to economic growth and convergence, focusing on the dynamics of cross-country income distributions. The traditional approach, which primarily uses cross-section regressions to estimate the relationship between growth rates and income levels, often fails to capture the complex dynamics of convergence. Quah argues that this approach overlooks the distinction between two key mechanisms: the growth mechanism, which increases aggregate output, and the convergence mechanism, which determines the relative performance of rich and poor economies. The paper highlights the importance of studying the entire cross-sectional distribution of economies, rather than just the steady-state behavior of individual economies. It introduces a new body of research that models the dynamics of these distributions, uncovering regularities such as persistence, stratification, and the formation of convergence clubs. These findings suggest that the world income distribution is polarizing into twin peaks of rich and poor, with middle-income groups vanishing. Quah emphasizes that traditional analyses, while technically correct, do not provide insights into the dynamics of convergence. In contrast, the new approach, which uses explicit models of distribution dynamics, offers a more nuanced understanding of how economies interact and how these interactions shape growth and convergence. The paper concludes by suggesting that the new theoretical ideas and empirical findings have significant implications for policy-making in areas such as regional development, economic redistribution, and comparative economic performance.This paper by Danny T. Quah, published in February 1996, critically reviews traditional and recent approaches to economic growth and convergence, focusing on the dynamics of cross-country income distributions. The traditional approach, which primarily uses cross-section regressions to estimate the relationship between growth rates and income levels, often fails to capture the complex dynamics of convergence. Quah argues that this approach overlooks the distinction between two key mechanisms: the growth mechanism, which increases aggregate output, and the convergence mechanism, which determines the relative performance of rich and poor economies. The paper highlights the importance of studying the entire cross-sectional distribution of economies, rather than just the steady-state behavior of individual economies. It introduces a new body of research that models the dynamics of these distributions, uncovering regularities such as persistence, stratification, and the formation of convergence clubs. These findings suggest that the world income distribution is polarizing into twin peaks of rich and poor, with middle-income groups vanishing. Quah emphasizes that traditional analyses, while technically correct, do not provide insights into the dynamics of convergence. In contrast, the new approach, which uses explicit models of distribution dynamics, offers a more nuanced understanding of how economies interact and how these interactions shape growth and convergence. The paper concludes by suggesting that the new theoretical ideas and empirical findings have significant implications for policy-making in areas such as regional development, economic redistribution, and comparative economic performance.