NEW YORK (AP) _ On July 17, bolstered by a stock market that seemingly knew no limits, 218 Americans could call themselves billionaires.

The subsequent market swoon since then, however, has forced almost 30 of them to turn in their billionaires club membership _ at least for the time being.

Forbes magazine's annual list of the 400 richest Americans, topped for the fifth straight year by Microsoft chief Bill Gates, includes a record 189 billionaires. But if the market had not turned south in mid-July, there would have been 29 more members of the billion-dollar bunch, Forbes said Sunday in releasing its Oct. 12 issue.

Among those who missed the cut to remain mere megamillionaires: Computer Associates chairman Charles Wang ($975 million); Walt Disney vice chairman and founder's nephew Roy Disney ($900 million); and the founders of the Yahoo! Web site, David Filo ($840 million) and Jerry Yang ($830 million).

With $58.4 billion, Gates remained far above No. 2 Warren Buffett _ even though Gates' net worth plunged $9 billion from the market's peak on July 17 to Aug. 31, when the Dow Jones industrial average tanked 512 points.

Of the top 10 on Forbes' list, all but two of the members earned their wealth from just two companies: Microsoft and Wal-Mart.

Investment guru Buffett, the head of Berkshire Hathaway, held second place with $29.4 billion. Behind him are Microsoft co-founder Paul Allen ($22 billion), Dell Computer chairman Michael Dell ($13 billion) and Microsoft president Steven Ballmer ($12 billion).

Rounding out the top 10 are the five heirs of Wal-Mart founder Sam Walton, each worth $11 billion.

Moving up fastest among the richest of the rich was Viacom chief Sumner Redstone ($6.4 billion), who leaped to 15th in the rankings from 37th, as the owner of Paramount Pictures, MTV and Blockbuster Video was rewarded by Wall Street.

On the down side, several big names tumbled down the list along with the market, including Oracle chairman Larry Ellison ($4.9 billion), who slid from 4th to 23th, and Nike chief Philip Knight ($3.5 billion), who dropped from 17th to 36th.

High-tech gurus were again prominent throughout the list, as were show-business heavyweights such as rival moguls Rupert Murdoch ($5.6 billion) and Ted Turner ($5 billion), directors George Lucas ($2 billion) and Steven Spielberg ($1.6 billion), and talk show queen Oprah Winfrey ($675 million).

Among those who fell from Forbes' roster this year are Netscape founder James Clark and chicken maven Frank Perdue.

In all, the combined net worth of the Forbes 400 is $738 billion, up from $624 billion in 1997 and $92 billion in 1982, the first year of the rankings.

The list also reveals a disturbing trend for parents and teachers trying to get their kids to concentrate on homework: 58 members of the Forbes 400 never finished college and carry an average net worth of $4.8 billion. The average wealth of Ivy Leaguers on the list? $2.3 billion.