Chapter 6 of my book "Database Nation: The death of privacy in the 21st Century", discusses privacy issues surrounding adoption and genetics. One of the key things that I learned when writing the book is that a large percentage of people in modern society are mistaken about the identity of their father.
How many? We're not sure. Here are some more recent articles that look at the question:
- The Conversation: What are the chances that your dad isn’t your father?, reports that estimates range from 9% to 30%.
- The Atlantic reports in 2007 that genetics students in graduate school are taught that the numbers are 5% to 15%, but substantially lower in some populations.
- Discover reports in 2010 that these numbers are vastly inflated.
- UNSW Sydney reported in 2014 that estimates range from 10% to 30%.
- Mean's Health in 2007 has a long article on the topic.
- Wikipedia's article is quite bland. You should improve it.