Sex surveys based on random samples from national population registers have been conducted in Finland in 1971, 1992, 1999, and 2007. They are representative of the total population within the age range of 18-54 years in 1971 and 18-74 years in 1992, 1999, and 2007. Sex survey in 1971 was only the second sexuality study in the world ever that was based on a representative national population sample.

Studies were conducted in 1971 and 1992 by individual face-to-face interview visits during which each interviewee also completed a self-administered questionnaire. Due this technique response rates were very high: in 1971 93% and in 1992 76%. In 1999 and 2007 a mail survey was conducted. The implication of this renewed method was lower response rate, in 1999 46% and in 2007 43%.

By analyzing the distributions in parallel generations of several identical retrospective questions measuring sexual issues in these four surveys it was possible to show that the lower response rate in 1999 and 2007 (due to renewed data collection technique) did not have a major impact on the results from the sexual histories of women and of those men who were less than 55 years of age. In the 55-74 years old age group, the male respondents were more monogamous than the corresponding birth cohorts interviewed in 1971 and 1992.

The main trends in sexual patterns and sexual attitudes from 1971 to 2007 will be presented.