Both of the candidates for the White House champion themselves as fighting for the middle class. They have also pointed fingers at one another for the erosion taking place in this weak pocket of America.

The Pew Research Center just released a new study that shows the middle class has thinned out over the last few decades. In the 1970s, the middle class represented nearly 61% of adults compared to only 51% at the end of 2011.

The new study looked at perceptions and financial data of those in the middle class from 1970 to 2011. It looked specifically at those that entered the class, those that fell out or moved up, views on politics, the economy and the outlook for the future.

Hispanic, Asian and Black college students and others with just a high school diploma were ones that lost the most ground over the last decade. Part of the reason for the downturn was the crash of the housing market that took place during the financial crisis and the lowering of the median household income for just the first time since the end of World War II.

The definition in the U.S. of middle class has varied at times. A conservative think tank, The Heritage Foundation, describes the U.S. middle class as a group of 60% who do not fall in the lower 20% and are not in the higher 20%. If that categorization were used, the income annually for a middle class household in the U.S. would be from $25,000 to $100,000.

The Pew study used socioeconomic categorization by individuals themselves and ended with average of $70,000 income for a family of four. The average annual income in the U.S. taken from census data is $68,275. The net worth of the middle class fell by 28% from 2007 to 2010 thanks to the financial crisis. The losses erased nearly 20 years of gains said the Pew Study.