Flip-flops achieved the same popularity the Birks had among Generation Xers .
In the United States , Birkenstocks were first popular among young adults , a group traditionally associated with American liberalism ; New York Times article : Thank You for Insulting Our Sandals ; in the early 1990s `` Birks '' were as popular among college-aged Generation Xers as flip-flops are in the 2000s .