An analyst, Michael Walkley, at Canaccord Genuity claims that Samsung outsold Apple smartphones in the U.S. in May. The claim is based on data that Walkley collected from store surveys. Apparently the Galaxy S4 was the top selling smartphone at Verizon, T-Mobile and Sprint. On AT&T it was the second best selling smartphone, second only to Apple iPhone 5. The Korean manufacturer has seen overwhelming demand for this smartphone, which actually is the fastest selling Android smartphone of all time.
The credit for this feat doesn't exclusively go to Galaxy S4.
Ubergizmo , Samsung Outsells Apple In U.S. Thanks To Galaxy S4 [Analyst], Samsung Outsells Apple In U.S. Thanks To Galaxy S4 [Analyst]