How often do men not tell their kids they used anonymous donor sperm?

Great question: I believe that over time when the children are old enough to understand that a majority of men well let their child or children know that they were conceived through donor insemination. Possibly to keep this a secret over time would be detrimental to the emotional relationship that is formed between parent and children.

Disclosure % ?: I'm not sure the percentage of parents who disclosure vs. those who do not. If you are stuck on whether to disclose or not, meet with a psychologist in the field. They can give you a lot of food for thought that will help you and your partner make a more informed decision. Usually one session can help address this kind of question.