Laputan Logic has some amazing graphs (scroll to The History of Naming entry) that show relative popularity of male names since XIV century and up to the year 2000.
"The graphs below show the ranking order of the top twenty names over time. While ranking doesn't convey a sense of relative population sizes, names like many things follow a power law distribution. During most of the period, at least up until 1800, 25% of the male population had the top ranked name, 50% had one of the top three names and over 80% had one of the top ten names."
