Paul Glamou | Aurora | Getty Images Harvard University

Harvard Business School graduates are flocking to Wall Street in numbers not seen since 2008 — which could be a very bad sign for the markets.

Around 38 percent of this year's HBS class took jobs in "market-sensitive" industries including investment banking, hedge funds, venture capital and private equity, up from just 31 percent last year. (You can look at the HBS data right here.)

For years, a consultant named Ray Soifer has analyzed the career paths of freshly minted Harvard MBAs looking for signs of the economy.

According to Soifer, when more than 30 percent of HBS grads take Wall Street jobs, it's a strong sell signal.

It's not precise timing. Soifer's HBS indicator first flashed a sell signal in 2005, years before the market came crashing down. It peaked in 2008, when 41 percent of the Harvard MBAs went to Wall Street.

This year saw a huge growth in the number going to hedge funds, from 4 percent of the class of 2010 to 7 percent in the class of 2011.

Private equity also expanded rapidly, from 9 percent to 14 percent.

The share going to investment banks and investment management held steady, at 10 percent. Venture capital's share actually shrank, from 3 percent to 1 percent. So perhaps talk of a tech bubble has gone too far.

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