1. Introduction

This chapter describes the different notions of cross-section and time-series convergence as well as presents a brief literature review of the main studies in the field of convergence and a brief account of their results. It also motivates the present study that investigates the existence of stochastic and deterministic convergence of real output per worker and its sources in 21 OECD countries over the period 1970–2011. It argues that the application of a large battery of panel unit root and stationarity tests, all robust to the presence of cross-sectional dependence, enables us to be more confident that non-rejections of the null of a unit root are not caused by the low power of conventional unit root tests of the ADF-type. A major novelty of our study compared to previous ones is that we investigate the existence of convergence patterns in the series of physical capital per worker, human capital, total factor productivity and average annual hours worked, which constitute the main sources of output.