Retail sales rose faster in April than they had in a year, the U.S. Census Bureau reported. Some retailers, though, are having a really tough time of it, with Macy's, Nordstrom and Kohl's all reporting disappointing first quarters and experiencing big share price declines.

This juxtaposition of rising retail sales and struggling retailers is nothing new. Overall retail sales have risen year-over-year every month for the past five years. Brick-and-mortar retail traffic, as measured by Prodco's weekly index, has been down year-over-year in 209 of 260 weeks over that period.

If the department stores, mall retailers and other businesses in the retail traffic index are seeing declining traffic, where are the increasing retail sales come from? Here are the four major categories with the biggest year-over-year gains in April, plus motor vehicles and parts, which had experienced strong sales growth until recently.

So ... Americans are going to the drugstore, the home improvement center and the bar down the street. And they're buying stuff online -- that's what "nonstore retailers" mainly means. It's no big surprise that they've taken market share away from brick and mortar. But it's telling that their sales gains seem to be accelerating, not slowing down.

Justin Fox is a columnist writing about business. Prior to joining Bloomberg View, he was the editorial director of the Harvard Business Review. He is the author of “The Myth of the Rational Market.” Fox has also worked at Time, Fortune, American Banker, the Birmingham News and the Advance-Register of Tulare, California, where he was the farm editor.