and/or has had sexual relations with the same sex may be underestimated in surveys that employ live interviewers to collect data. Their argument is that methods stronger in anonymity and/or confidentiality, such as online questionnaires and IVR interviews, are better than more traditional survey modes at gauging the size of the non-heterosexual population. British researchers with the third wave of the National Survey of Sexual Attitudes and Lifestyles (NATSAL) addressed this matter in one of their studies. Interviewers collected data on sexual behavior from a sample of over 15,000 subjects at their home. However, a portion of respondents agreed to complete an online questionnaire asking many of the same questions asked live before. The questionnaire was to be taken one to two months after the original interview. The data below were extracted from the same group of 202 men and 325 women who gave out information about same-sex experiences live and then successfully completed the online questionnaire later. Numbers show how answers varied between survey modes and the information is given on whether the difference between methods was significant or not. Researchers from other countries have produced similar findings. In Poland, for example, it was found in an experiment that self-reporting same-sex attraction was twice as common using an online questionnaire as in a paper questionnaire, despite the fact that the group that answered the online questions and the one that filled out the paper form were similar on all demographic variables and on all other aspects of their sexuality. In the 90s, an experiment was made in the US where it was found that teen males were several times more likely to acknowledge same-sex experiences using a computer methodology compared to paper questionnaires. Change in prevalence over time In addition, shifts can occur in reports of the prevalence of homosexuality. For example, the Hamburg Institute for Sexual Research conducted a survey over the sexual behavior of young people in 1970 and repeated it in 1990. Whereas in 1970 18% of the boys ages 16 and 17 reported to have had at least one same-sex sexual experience, the number had dropped to 2% by 1990. Data from the General Social Survey shows that the percentage of Americans reporting predominantly same-sex partners remained stable between 1989 and 2014. In contrast, the percentage who reported ever having a same-sex partner increased. By contrast, the National Survey of Family Growth has found an