San Jose, Calif. ? In the most highly anticipated Wall Street debut since the heady days of the dot-com boom, shares of Google surged nearly 20 percent on their first day of public trading Thursday as the quirky Internet company completed its much-hyped initial stock offering.

Despite the first-day jump, the debut generated much less money than the company envisioned after it launched an unorthodox auction designed to open the stock beyond large investors who typically get first crack at new stock issues.

Google shares finished the day at $100.34, up 18 percent, and the stock offering raised $1.67 billion. The company originally hoped to open at between $108 and $135, generating as much as $3.6 billion and making the company worth up to $36 billion.

“If it’s not a failure, it clearly didn’t work the way Google’s management intended it,” said Barry Randall, portfolio manager for the First American Technology Fund.

Still, the IPO makes the company worth 27.2 billion, on par with General Motors.

And it brought instant riches to hundreds of employees of a company that was dreamed up in a college dorm room in 1998. In true dot-com fashion, a scheduled summer picnic planned for today near Google’s Mountain View, Calif., headquarters is expected to turn into an IPO party.

About 1,000 of Google’s nearly 2,300 employees are now millionaires on paper, according to an analysis done by Salary.com, which tracks employee compensation.

“There are going to be some pretty good parties in the Bay area this evening — probably not a lot of work getting done at Google tomorrow,” said Bill Coleman, the firm’s senior vice president of compensation.

The offering also made co-founders Sergey Brin and Larry Page billionaires — at least on paper. From share sales in the IPO, Page collected $41.1 million and Brin got $40.9 million, but that pales in comparison to the more than $3 billion each still holds in Google shares.

But celebrations are likely to be more muted in the offices of Google’s underwriters, who will share just $46.7 million for handling the stock offering, according to a filing Thursday. That is just a 2.8 percent commission, a fraction of the typical 7 percent they usually receive.

The sign outside the Nasdaq market shows a picture of the representatives from Google attending the Internet search engine's initial public offering in New York. Initial shares of Google Inc. were priced late Wednesday at 5, but closed 18 percent higher Thursday at 00.34.

Google’s price was set Wednesday after the close of an unusual auction in which would-be investors bid how much they thought the search engine to be worth. All winning bidders paid the same price — one that guaranteed the sale of all 19.6 million shares.

Though the so-called Dutch auction was designed to open the IPO beyond large investors, that is not what actually happened, said David Garrity, a technology analyst in New York with Caris & Co.

Investors needed large bank accounts to qualify for the auction, and international investors were barred from participating. And others might have been scared by Google’s initial per-share price estimate.

“It was supposed to democratize the process and let people buy in at just a few shares, but it was a miserable failure because the organizers didn’t realize the securities regulations that require people who bid to have a certain net worth,” said David Garrity, a technology analyst in New York with Caris & Co.

Most analysts expect Google’s stock price to be volatile, both because of missteps leading up to the IPO and its executives’ statements on how they run the company.

Since Google’s first filed to go public, it has painted itself in regulatory filings as an untraditional company. Its leading position as a search engine and hot stock prospect quickly led unprecedented attention that both revealed several warts and raised doubts about its executives.

Before any shares were sold, the company announced that it was the subject of regulatory attention for failing to register pre-IPO stock and options as well as an interview in Playboy magazine by its founders. That happened during the so-called quiet period.

Now, investors must both digest the implications of those missteps and the company’s structure.

The company also faces stiff competition — from small startups like Vivisimo to tech titans like Yahoo and Microsoft, which have been beefing up search features on their sites.

“Google came out of nowhere and it’s entirely possible that the next big competitor could come out of nowhere, too,” said Tara Calishain, co-author of “Google Hacks” and author of the soon-to-be-released “Web Search Garage.”