"Working Americans have long complained about a middle-class squeeze........EPI data tracking income and wage patterns show that the majority of income growth has for decades gone to a startlingly small number of top earners, while other workers have suffered a persistent stagnation or even decline in real earnings. While many middle-income families have lost jobs, homes, and retirement savings during the latest recession, their economic woes date back much further.
This pattern is best illustrated in the following chart, which shows that 34.6% of all income growth over the past three decades has gone to the top one-tenth of 1% of all earners. By contrast, the bottom 90% of all earners has collectively seen only 15.9% of all income growth over the same period...."

The State of Working America shows that the highest-paid workers do not just earn more, but enjoy far greater income growth than the bottom 95%:

"And it shows that this general wage stagnation has occurred even as the country has enjoyed large gains in productivity:"
http://www.epi.org/analysis_and_opinion/entry/a_long_and_persistent_middle-class_squeeze/