(John McDonnell/The Washington Post)

Amid the talk of the NFL one day putting an expansion team in London, Nate Silver of ESPN’s fivethirtyeight.com offers a compelling argument for why the league might want to first consider a few cities closer to home.

Looking at cities that already have NFL teams and a few potential expansion markets for his analysis, Silver multiplied a metro area’s population by the volume of Google searches it conducts for NFL-related topics. He then calibrated the estimate of NFL fans in a given metro area to the U.S. average of 28 percent who say they are avid NFL fans.

The largest estimated NFL fan bases are in New York (5.45 million), Los Angeles (3.66 million) and Chicago (2.7 million). Five of the top six metro areas already have NFL teams, with L.A. being the exception. Mexico City ranks seventh, despite the fact that  only seven percent of its population is estimated to be NFL fans.

Washington, D.C. is ninth, sandwiched between Miami and Phoenix, with an estimated fan base of 1.38 million. Silver’s method suggests 29 percent of the D.C. metro area’s 4.79 million residents are NFL fans.

Baltimore’s estimated fan base (850,000) ranks 18th, three spots below Toronto, but 38 percent of the Baltimore metro area’s 2.26 million people are NFL fans, the highest percentage in Silver’s study.

Los Angeles, Mexico City and Toronto are the only cities without NFL franchises in the top 20. Las Vegas (22), Sacramento (28), Virginia Beach-Norfolk (30) and San Antonio (31) all rank above London (33).

The smallest estimated fan bases in metro areas that have NFL teams are Nashville (230,000), Jacksonville (290,000) and New Orleans (290,000).

Check out Silver’s full list here.