According to baby name blogger Laura Wattenberg

Historically, names in the English-speaking world were a relatively constrained set, with a small collection of classic names dominating. In England in 1800, the top six names for boys and girls accounted for more than half of all babies born….

By 1950 in the United States, you needed 79 names…to get the same population coverage that those six names achieved in England in 1800. Today, it would take 546 different names…

(via Live Science, TYWKIWDBI)