Since several years EIM Business and Policy Research maintains a data base on business ownership rates across OECD countries, called COMPENDIA (COMParative ENtrepreneurship Data for International Analysis). EIM harmonizes raw numbers of business owners (self-employed), as published in the OECD Labour Force Statistics, towards a uniform definition. We define the business ownership rate as the number of owner-managers of unincorporated and incorporated businesses, as a fraction of the total labour force.

Until recently, data in COMPENDIA were published for a group of 23 OECD countries, starting from 1972 onwards. However, in the most recent version of the data base time series for seven additional countries have been introduced for the first time, so that the COMPENDIA data base now covers 30 OECD countries. The current paper makes four contributions. First, we provide an update of the methodology used to harmonize business ownership rates across countries. In doing so, as a second contribution, we provide two extended country cases (Poland and the United States) which illustrate the many methodological pitfalls that have to be dealt with when measuring the number of business owners. Third, we present business ownership time series for 30 OECD countries including the new countries in our data base: Czech Republic, Hungary, Korea, Mexico, Poland, Slovak Republic, and Turkey. Fourth and finally, we pay considerable attention to the sizable differences in the level and development of business ownership since 1989 in four Central and East European transition economies in our data base: Czech Republic, Hungary, Poland, and Slovak Republic.