In addition to the above links, it is possible to do quite a lot of research on the subject of sexual orientation identification at various ages. A good introduction is at the National Institute of Health's Gay and Lesbian Health pages. These have links to information on coming out, social issues, etc., such as the American Psychiatric Association's page, Gay, Lesbian and Bisexual Issues. You can also get abstracts of highly technical and scholarly papers, using Pubmed. The search: "coming out" and midlife gets 70 hits. "gender identity" and midlife and women and statistics gets 243, but clicking the "limits" tab and checking "free full text" and re-entering that search gets 13 hits. In each full record (click on the full text icon to the left of the title in the list), you will need to click again on a Full Text button in the upper right. This will take quite a bit of trial and error, because full text search finds words and phrases that are used only in passing. Limiting to women, and to "title/abstract", still limiting to "free full text online", the search: "sexual orientation" and age gets 15 hits.