The combined net worth of the 2012 class of the 400 richest Americans is $1.7 trillion, up from $1.5 trillion a year ago. The average net worth of a Forbes 400 member is a staggering $4.2 billion, up from $3.8 billion, and the highest ever, as two-thirds of the individuals added to their fortunes in the past year.  Another factor: the gap between the very rich and the merely rich is widening. Only two in the top 20 are poorer, and as a group they are worth $73 billion more than a year ago.

The country’s three richest entrepreneurs drove much of those gains, continuing to add billions to their net worth, even as they give money away. Bill Gates, Warren Buffett and Larry Ellison, who hold onto their respective spots at numbers 1, 2 and 3, were up $7 billion, $7 billion and $8 billion, respectively.  Ellison’s $8 billion jump was the biggest dollar gain of anyone on the list this year. Pals Gates and Buffett are also the most generous people on the planet, having given $28 billion and $17.5 billion to date, respectively, including $1.5 billion that Buffett gave away since the last rich list.

The combined net worth of the 2012 class of the 400 richest Americans is $1.7 trillion, up from $1.5 trillion a year ago. The average net worth of a Forbes 400 member is a staggering $4.2 billion, up from $3.8 billion, and the highest ever, as two-thirds of the individuals added to their fortunes in the past year.  Another factor: the gap between the very rich and the merely rich is widening. Only two in the top 20 are poorer, and as a group they are worth $73 billion more than a year ago.

The country’s three richest entrepreneurs drove much of those gains, continuing to add billions to their net worth, even as they give money away. Bill Gates, Warren Buffett and Larry Ellison, who hold onto their respective spots at numbers 1, 2 and 3, were up $7 billion, $7 billion and $8 billion, respectively.  Ellison’s $8 billion jump was the biggest dollar gain of anyone on the list this year. Pals Gates and Buffett are also the most generous people on the planet, having given $28 billion and $17.5 billion to date, respectively, including $1.5 billion that Buffett gave away since the last rich list.