(MONEY Magazine) – A decade ago Harry Dent had the business book equivalent of the Macarena with The Great Boom Ahead. In it he predicted that baby boomers' peak spending years would create a decade of prosperity in the 1990s. Nice call.

Dent's latest, The Next Great Bubble Boom (Free Press, $26), hits shelves later this month. But like any one-hit wonder, Dent's act sounds old 10 years later. Now he says that the final wave of boomer spending before retirement will send the Dow to 40,000 by the end of this decade--and then to 7000 by the end of the next.

The biggest hole in Dent's argument is his lack of faith in the market. Stock prices are set by the collective wisdom of millions. If a falloff in boomer spending is going to hurt profits in 2010, that'll hold down prices today.

If Dent's analysis is right, stocks are in for a long, slow fall, not a boom. His retort: "If the market's so smart, why did Internet stocks trade at 400 times earnings?" Uh, because the potential of new technology is much harder to quantify than demographic trends, that's why. Is there anyone who hasn't heard of the aging of America? --STEPHEN GANDEL