Previous research has described both theoretically and empirically, the negative consequences of having a politicized civil service, recruited on political instead of professional merits. However, we know fairly little about what explains politicization, especially outside the U.S. context. This study reviews literature in the field and identifies four commonly used explanations, and tests them on a study of agency heads in Sweden between 1960 and 2010. For this purpose, we have collected new data that includes information about 1836 Director Generals‟ political and/or professional back-grounds. Our study demonstrates that none of the previously used explanations – NPM reforms, ideological bias of the government, the number of years that the government has been in power, and the Parliamentarian support that the government enjoys – holds ground. Our general conclusion is therefore negative, and emphasizes the need for more systematic research on this matter
