Bill Gates keeps getting richer. And for the 20th year in a row, he's been named the richest man in America, according to the Forbes annual list which published on Monday.

This is all while he's hard at work with his philanthropy projects and his promise to give most of his wealth away. This time, it's not Microsoft which is contributing to his wealth.

Gates is worth $72 billion with Microsoft accounting for one-fifth of that, reports Forbes. Microsoft did help out in August, when Steve Ballmer announced he would resign.

The bulk of his money comes from his investment firm Cascade which owns a big chunk of tractor maker Deere & Co., as well as Canadian National Railway and Mexican Coke bottler Femsa.

Gates is $9.8 billion richer since the start of 2013, according to Bloomberg's Billionaire Index.

By some accounts, Gates has given away at least $28 billion away to charitable causes between 2007 and 2012, but clearly his wealth is still growing faster than he's giving it away.