"High net worth private client individuals who were reluctant to participate in the I.P.O. market a year ago are increasingly reallocating money towards equities," said Neil A. Mitchell, a managing director of equity capital markets at Credit Suisse.
This year, 169 companies have gone public in the United States, raising $45 billion, according to Thomson Reuters. Both figures are at the highest levels since the financial crisis of 2008, though the number of offerings remains below the level set before the financial crisis. And nine companies have raised more than $1 billion in their debuts so far in 2013, the largest number in at least five years.
"There's a willingness to pay for growth in a slow-growth economy," said Liz Myers, JPMorgan Chase's head of global equity capital markets.
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Still, while Internet offerings like Twitter may get much of the attention, the number of technology offerings actually ran at a multiyear low for much of this year. They now account for just 18 percent of all I.P.O.'s in the United States, according to Renaissance Capital.
The sector has shown signs of a recovery of late, with offerings like those of the cybersecurity provider FireEye and the advertising technology company Rocket Fuel. Both companies' shares closed on Friday at more than double their offering prices, with Rocket Fuel at $61.72 and FireEye at $41.22.
Indeed, technology offerings have had an average first-day return of 30 percent and a total average return of 47 percent, a sector performance bested only by the consumer industry, according to Renaissance.
That sort of reception from investors will no doubt steer more tech start-ups toward going public at some point.
"The level of tech financing right now is as high as we've seen it in the last 10 years," said Jeffrey Bunzell, the head of Americas equity capital markets at Deutsche Bank. "That's something we're expecting to continue into next year."
This year's two biggest offerings so far have been Plains GP Holdings, an oil-and-gas pipeline operator that raised $2.8 billion last week, and Zoetis, an animal health company spun off from Pfizer that raised $2.5 billion earlier this year, according to Thomson Reuters.
By comparison, Twitter is expected to raise as much as $1.4 billion in its I.P.O., and as much as $1.6 billion if its underwriters choose to sell further shares in what the industry calls a greenshoe.
That is unlikely to strain the stock market's ability to digest a major offering in the same way that Facebook's $16 billion stock sale did last year.
(Read more: Inside the NYSE's systems test before Twitter IPO)
"A deal like Twitter is large and important, but it's not a test of the I.P.O. market," said one underwriter, who was not authorized to speak publicly about the offering. "It's more a reflection of the health of the I.P.O. market and the attractiveness of the company."
An aspect of the Facebook offering that companies are trying their hardest to avoid is troubles on the first day of trading. Bankers blamed technical problems on the Nasdaq stock market as well as decisions to expand Facebook's offering price and number of shares sold to what some critics said were the highest possible levels. That prompted a number of investors to sell when the stock experienced trouble trading.
Now, underwriters say, companies are more willing to price their offerings slightly lower to ensure that their shares trade well from the start. That means occasionally putting up with big "pops," or significant jumps in price on the first day of trading: Rocket Fuel and FireEye both doubled their offering prices in their first day of trading last month. Such sharp rises suggest that companies raised less than was possible.
Twitter itself is planning to sell its shares at $17 to $20, less than what many optimistic analysts had expected. Company executives may raise that price if they find exuberant demand in their week-and-a-half trip across the country.
The company and its advisers will spend the next nine days traveling to major cities like New York, Boston, Chicago and Los Angeles, meeting with institutional investors like mutual funds and hedge funds. On Nov. 6, they will assemble the final order book determining the final price and size of the offering.