PIP: Changing marriage patterns in the Netherlands are described. The author notes that although the popularity of marriage at younger ages has declined rapidly in recent years, cohabitation at the same ages has increased significantly. By the end of the 1980s almost one-half of women aged 18-37 with a partner had lived in a consensual union at some time. The author concludes that consensual union before marriage is likely to become the norm during the 1990s. (SUMMARY IN ENG)