For example, if I have sex with a girl born in Greece, two girls born in Poland, one from Colombia, and a ton from the United States, I have four flags. Most American guys have flags in the low single digits while some multilingual friends are in the high single digits. I have only met two men who are in the double digits, and prolonged travel seems to help. It may even game the metric a little unfairly. Still, the number gives you a rough snapshot that is hard to fake.