A large number of potential determinants of union membership, which often can be interpreted in terms of costs and benefits, have been incorporated into economists' traditional supply and demand framework or into new models of an individual's decision to unionise (such as social custom theory)....

Using data from the social survey ALLBUS for West Germany in the period 1980 to 2006, this paper demonstrates that union members are on average older than non-unionized employees. The probability of being unionized shows the inverted U-shaped pattern in age conjectured by Blanchflower (BJIR...