StumbleUpon has modestly overtaken Facebook in sending traffic to U.S. websites during the past month, but not globally.

StatCounter Global Stats shows StumbleUpon taking a roughly 20 percentage point lead over Facebook in sending traffic to U.S. websites only during the last month, but globally Facebook’s has almost three times that lead over StumbleUpon.

Get a load of the charts below comparing global and U.S. web traffic. Do you think the pattern that has emerged over the past month in the U.S. will continue or reverse course?