According to Forbes, the richest 400 Americans’ net worth increased 13 percent in 2012 to $1.7 trillion. The average net worth of the group was also up to a record $4.2 billion, and collectively they make up the equivalent of one-eighth of the U.S. economy. So who makes the cut? Bill Gates tops the list for the 19th year in a row, with a net worth of $66 billion, followed by Warren Buffett ($46 billion), Larry Ellison ($41 billion), and the Koch brothers tied for fourth at $31 billion. Bucking the trend of increases is Facebook CEO Mark Zuckerberg, whose net worth fell by half to just $9.4 billion and slid to No. 36 on the list from No. 14 in 2011.

The wealth gap between the richest Americans and the typical family more than doubled over the past 50 years.

In 1962, the top 1% had 125 times the net worth of the median household. That shot up to 288 times by 2010, according to a new report by the Economic Policy Institute.

That trend is happening for two reasons: Not only are the rich getting richer, but the middle class is also getting poorer.

Most Americans below the upper echelon have suffered a decline in wealth in recent decades. The median household saw its net worth drop to $57,000 in 2010, down from $73,000 in 1983. It would have been $119,000 had wealth grown equally across households.

The top 1%, on the other hand, saw their average wealth grow to $16.4 million, up from $9.6 million in 1983. This is due in large part to the growing income inequality divide, as well as the sharp rise in value of stocks over the period.

Of course, we've all known this, except for perhaps these most recent precise numbers.