The Maddison Project, initiated in March 2010 by a group of close colleagues of Angus Maddison, aims to develop an effective system of cooperation between scholars to continue Maddison's work on measuring economic performance in the world economy. This article is a first product of the project. Its goal is to explain the aims and approach of the project, and, as a first result of this ‘collaboratory’, to inventory recent research on historical national accounts. We also briefly discuss some of the problems related to these historical statistics and we extend and where necessary revise the estimates published by Maddison in his latest overviews. Most new work relates to the period before 1820; it leads to a reassessment of levels of GDP per capita in western Europe in the early modern period, and to a confirmation of Maddison's previous estimates of Asian levels of real income.