Records kept by the U.S. Social Security Administration reveal that knowing someone's first name is a great clue to learning what decade they were born.

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Popular names in the 1940s and 1950s were Mary, Linda and Lisa for girls and James, Robert and Michael for boys, The Baltimore Sun reports.

Those names didn't even make the Top 10 list last year when popular names for girls were Emily, Olivia and Madison and for boys were Jacob, Christopher and Ethan.

Susan Bartolini, a school nurse in Baltimore, says she meets a lot of children with names that could be either male or female such as Taylor, Alex and Sydney.

Since the 1970s, picking unusual names has been a trend in black communities, especially for girls.

Researcher Steven Levitt writes in Freakonomics that nearly 30 percent of black infant girls are given a name that is unique among every baby born that year in California.