An economy may be measured in many ways. But the percentage of Americans who say they are in the middle or upper-middle class has fallen 10 percentage points, from a 61% average between 2000 and 2008 to 51% today. See here.
The reality is even worse: only 20% of American households actually possess the income and assets that characterize the middle class in financial terms. Decades of savings-robbing government programs such as Social Security and Medicare have robbed the American people of their financial substance.