The Times has a front-page article...

...today titled, "The Middle Class Is Steadily Eroding. Just Ask the Business World." It argues that the proof of the pudding is in the eating (my emphasis):

As politicians and pundits in Washington continue to spar over whether economic inequality is in fact deepening, in corporate America there really is no debate at all. The post-recession reality is that the customer base for businesses that appeal to the middle class is shrinking as the top tier pulls even further away.

PricewaterhouseCoopers clients like big stores and restaurants are chasing richer customers with a wider offering of high-end goods and services, or focusing on rock-bottom prices to attract the expanding ranks of penny-pinching consumers.

In 2012, the top 5 percent of earners were responsible for 38 percent of domestic consumption, up from 28 percent in 1995, the researchers found.

Even more striking, the current recovery has been driven almost entirely by the upper crust, according to Mr. Fazzari and Mr. Cynamon. Since 2009, the year the recession ended, inflation-adjusted spending by this top echelon has risen 17 percent, compared with just 1 percent among the bottom 95 percent.