"With a combined worth of $2.34 trillion, the Forbes 400 own more wealth than the bottom 61 percent of the country combined, a staggering 194 million people. The median American family has a net worth of $81,000. The Forbes 400 own more wealth than 36 million of these typical American families."

http://www.ips-dc.org/billionaire-bonanza/

According to that article, the 1% are worth around $26 trillion. So to answer the Muffin's question, looks like the 400 have just over 10% of the 1%er wealth.

That quote also included the comparison to the median family net worth.

The quote says, "... the bottom 61 percent of the country combined, a staggering 194 million people." It's not comparing the number to the world's population.

Looks like about 1.9%

Estimates put the total net worth of the world's richest 1% at 140 trillion.

The Forbes 400 has about 2.7t net worth.