Life is good for America's super wealthy.
Forbes on Monday released its annual list of the top 400 richest Americans.
While most of the top names and rankings didn't change from a year ago, the majority of the elite club's members saw their fortunes grow over the past year, helped by strong stock and real-estate markets.
"Basically, the mega rich are mega richer," said Forbes Senior Editor Kerry Dolan.
Dolan noted that list's minimum net income increased to a pre-financial crisis level of US$1.3 billion, up from US$1.1 billion in 2012, with 61 American billionaires not making the cut.
"In some ways, it's harder to get on the list than it ever has been," she said.
Microsoft Corp co-founder Bill Gates remains America's richest man, taking the top spot on the list for the 20th straight year, with a net worth of US$72 billion, up from US$66 billion a year ago.
Investor Warren Buffett, the head of Berkshire Hathaway Inc, posted another distant second-place finish with US$58.5 billion, but increased his net worth from US$46 billion.
Oracle Corp co-founder Larry Ellison stayed third with US$41 billion and was the only member of the top 10 whose net worth was unchanged from a year ago.
Brothers Charles and David Koch, co-owners of Koch Industries Inc, stay tied for fourth with US$36 billion each, up from US$31 billion in 2012.
Wal-Mart heirs Christy Walton, Jim Walton, Alice Walton and S. Robson Walton took the next four spots, with holdings ranging from US$33.3 billion to US$35.4 billion, all increasing from year-ago levels. New York City Mayor Michael Bloomberg, the founder of the eponymous financial information company, rounds out the top 10 with US$31 billion, up from US$25 billion.
According to Forbes, 273 members of the list are self-made billionaires, while 71 inherited their wealth and another 56 inherited at least some of it, but are still growing it.
Facebook CEO Mark Zuckerberg returned to the list's top 20 after dropping out the year before. His net worth of US$19 billion earned him the No. 20 spot.
Facebook co-founder Dustin Moskovitz also made the list at No. 85,with a net worth of US$5.2 billion. At age 29 and just a few days younger the Zuckerberg, Moskovitz ranks as the youngest member of the list.
On the flip side, the oldest person on the list is 98-year-old David Rockefeller Sr at No. 193 with a net worth of US$2.8 billion.
A total of 20 new people joined the rankings, while 28 people dropped off the list, including six who died.
A total of 48 women made the list including Hyatt Hotels heir Jennifer Pritzker at No. 327. Formerly known as James Pritzker, she's the list's first transgendered member.
According to Forbes, the 400 people on the annual list posted a combined net worth of US$2 trillion, up from US$1.7 trillion a year ago. That marks their highest combined value ever.
average net worth
Meanwhile, the average net worth of the list's members rose to US$5 billion, also the highest ever, up from US$4.2 billion in 2012. Net worth grew for 314 members and fell for 30, Forbes said.
The increases aren't surprising, given that net worth for 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.
According to a study of Internal Revenue Service figures released last week, the top one per cent of US earners collected 19.3 per cent of household income in 2012, their largest share in IRS figures going back a century.
Some economists have speculated that the incomes of the wealthy might have surged in the past year, because they cashed in stock holdings to avoid higher capital gains taxes that kicked in in January.