Determinants of the increase in the number of interest groups in western democracies: Theoretical considerations and evidence from 21 OECD countries

Mancur Olson's theory of institutional sclerosis is based on the notion that the number of interest groups within a country increases with the duration of its political stability. The following paper argues that the increase in the number of interest groups over time could also be a concomitant of economic development. Theoretically, both explanations prove tenable. An empirical cross-sectional regression analysis using data from 21 OECD countries finds no evidence for a significant impact of the duration of political stability on the number of interest groups. A significantly positive effect is, however, reported for the degree of economic development.