When will the tech bubble burst?

It is true that prices today are not quite as widely overvalued as in 1999. Large technology stocks are up 350 percent this decade, the low end of the range for the hot stocks from earlier booms, which saw gains of 300 to 1,900 percent. Only a few select technology companies — mainly the internet giants — are trading close to the valuations of the dot-com era, when the average price-to-earnings ratio for tech companies hit 50. The average ratio for that sector today is 18.

However, the scale of today’s tech boom is not readily visible because much of the investment action has moved into the hands of big private players. In 1999, nearly 550 start-ups went public, and after many ended in disaster, the government tightened regulation of public companies. In part to avoid that red tape, this year only 11 tech companies have gone public. Many are raising money instead from venture capitalists or private equity funds. Venture capitalists have poured more than $60 billion into the technology sector every year for the past three years — the highest flows since the peak in 2000 — and private equity investors say there has never been a better time to raise money.