Bill Gates stays atop Forbes list of richest Americans for the 21st straight year

Microsoft co-founder Bill Gates topped Forbes' latest list of the 400 richest Americans for the 21st straight year.

The list, released on Monday, was largely unchanged for 2014 and showed the rich getting richer. The combined wealth of those on the list rose 13 percent to $2.29 trillion, helped by a stronger U.S. stock market.

Gates' net worth totaled $81 billion, up $9 billion from 2013.

Investor Warren Buffett, the head of Berkshire Hathaway Inc., remained in second place at $67 billion. Oracle Corp. co-founder Larry Ellison also kept his No. 3 spot with $50 billion.

Brothers Charles and David Koch, co-owners of Koch Industries Inc., stay tied for fourth with $42 billion each.

There were 27 new members of the list, including WhatsApp co-founder Jan Koum in the 62nd spot. Facebook announced plans to buy the mobile messaging app for $19 billion in February.

The biggest gainer is Facebook CEO Mark Zuckerberg, No. 11, whose net worth grew $15 billion since last year to $34 billion.

The net worth of America's wealthiest people has risen in the years since the financial crisis, widening the gap between the exceptionally well-to-do and the rest of the country. The average net worth of a Forbes 400 member is $5.7 billion, up from $5 billion last year.