According to Stefan Marschall, the post-World War II years, particularly the 1980s and 1990s, saw tremendous growth in parliamentary assemblies, with more than 40 established since 1949. About 42% of the world's parliamentary assemblies are formally affiliated with an intergovernmental organization; 32% are informally affiliated; and 26% are unaffiliated. The spread in parliamentary assemblies was spurred by acceptance of parliamentarism as a means of legitimizing decisions; initiatives for intergovernmental cooperation reaching a point at which stronger parliamentary backing was needed; and regional integration. However, many global organizations, such as the UN and WTO, still lack a parliamentary assembly and "have been heavily criticized for what is supposed to be an institutional deficit."