A billion dollars just doesn't go as far as it used to. For the first time, it takes more than $1 billion to earn a spot on Forbes magazine's list of the 400 richest Americans.

The minimum net worth for inclusion in this year's rankings is $1.3 billion, up $300 million from last year.

The new threshold means 82 of America's billionaires didn't make the cut. Collectively, the people who made the new rankings are worth $1.54 trillion, compared with $1.25 trillion last year.