ORGANIZING THE BOYS OF SUMMER - THE EVOLUTION OF US MINOR-LEAGUE BASEBALL, 1883-1990

The authors use life-history data to analyze the organizational evolut ion of U.S. minor-league baseball. The article introduces the concept of ''structural mutualism'' to account for the structural effects of r equired league membership on team foundings and deaths. This term refe rs to cooperative behavior that occurs among the teams within a league , that benefits each team, and that league membership promotes. Net of conventional density-dependence and population-dynamics mechanisms, s trong evidence is found that structured mutualism affects team foundin gs and deaths. When structured mutualism is conceived of as variable, the concept may have more general applicability to other sets of membe rship organizations.