NEW YORK — There's even more proof that the rich are getting richer while everyone else gets poorer.

In a new report, Pew Research Center said Wednesday that the gap between the nation's wealthiest households and middle- and low- income earners is the widest it has been since the government began collecting data 30 years ago.

Pew, which analyzed Federal Reserve data, said the median wealth of upper-income families was $639,400 in 2013. Middle-income households were worth $96,500, while low-income families were worth $9,300. Pew calculated wealth by adding a family's assets, including homes, cars and businesses, and subtracted it from debts.

To qualify as middle income, Pew said that a family of three needs to make $38,100, while to qualify as upper income, that same size family would need to earn $114,300. It adjusted that number based on the size of a family. Families of five, for example, need to earn $49,200 to be middle income and $147,600 to be considered upper income.

Upper-income families were the only ones to increase their wealth between 2010 and 2013, Pew said. The wealth of middle-income families was unchanged during that time and the wealth of low-income families fell.