A consumer spending recovery has stalled for most Americans -- but not for the rich. Upper-income Americans increased their buying by an amazing 33% in May, according to Gallup. Meanwhile, spending was flat for everybody else. What's going on here?

First, let's look at the charts Gallup provides. First, for the upper-income consumers:

And then for the lower- and middle-income consumers:

As you can see, each group spent very differently in May. For upper-income consumers, Gallup says that $145 per day is the highest monthly average since November 2008. May's spending was 33% higher than both a month and year prior.

But for everybody else, spending remained subdued. In May it was flat at $59 per day versus a month and year earlier. It was only a dollar higher than in March. So what's driving the wealthy to spend but the low- and middle-income Americans to refrain from making additional purchases?

It wasn't the wealth effect. If the rich felt wealthier in May due to their investments doing well, then they might have felt more comfortable spending. Yet, if you look at the stock market, that doesn't seem particularly plausible. Stocks had a pretty rotten time in May, as the Dow declined by 8%. So anyone with a big stock portfolio actually would have felt poorer in last month.