What is the Net Worth of the Bottom 50% ?

The President’s remarks at the recent State of the Union aroused my curiosity:

Since my election, the net worth of the bottom half of wage earners has increased by 47 percent — three times faster than the increase for the top 1 percent.

Questions:

This prompted the following questions:

  1. So, what is the average net worth of the bottom 50% of Americans?
  2. How has the average net worth of the bottom 50% changed over time, adjusted for inflation, starting around 1970?
  3. For extra bonus points, can you compare that to data on the top 1%?

Follow-up:

This sounds like it would make a good story for  The Indicator from Planet Money.