In a speech in Washington on Thursday, the chairman of President Obama’s Council of Economic Advisers said that the American middle class has been shrinking since 1970. Princeton University economist Alan Krueger said the American middle class shrank from 50.3 percent of American households in 1970 to 42.2 percent in 2010. Krueger defined the middle class as households with annual incomes within 50 percent of the national median income. Here is a table presented describing his findings.