Apparently the movie 40 Year-Old Virgin
should have been set in Japan, if the new study
("Male and Female Life and Awareness") by the Japan Family Planning Association is to be believed. It found that "7.9% of the men in the 40-45 age segment claimed they have yet to experience sex."
That seems like an awfully high figure, and without knowing any details about the study (how were the questions phrased, how many people were questioned, etc.) it's difficult to know whether to take it seriously. Kunio Kitamura, director of the JFPA, blames this figure on poor male-female communication in Japan and widespread performance anxiety among Japanese men: "Their concerns, over things like being unable to achieve erection, or enabling their partner to reach orgasm, became so oppressive they decided to avoid sex altogether."
I've searched, but I can't find any more details about this study other than this lone article. (My lack of knowledge of Japanese obviously hindered my search.) But my gut feeling is that this study probably isn't too reliable.