Media playback is unsupported on your device Media caption The opening bell rings on the trading floor of the New York Stock Exchange as trading starts in Twitter shares

Shares in the microblogging site Twitter closed at $44.90, up more than 73% from their initial price of $26 each.

That means after its first day as a public company, Twitter is now valued at a little over $31bn (£19bn).

More than 13 million shares were traded once they became available an hour after the New York Stock Exchange opened.

It is the biggest technology listing since Facebook in 2012.

Twitter floated on the NYSE and not, as some initially expected, the technology-rich Nasdaq exchange, where the likes of Facebook are listed.

It was a big win for the NYSE, which decorated its exterior with banners promoting the offering on Thursday.

Twitter has more than 230 million users, but is yet to make a profit.

Image caption Many had expected Twitter to choose the technology-heavy Nasdaq exchange for its flotation

Image caption Head of the NYSE Duncan Niederauer oversees the action

Rollercoaster ride

Shares in newly listed companies are often volatile on their first day of trading.

Within minutes, Twitter's stock price soared more than 80% before closing just below its initial opening price of $45.10 per share.

The price is right - Analysis Shares in Twitter spiked almost 80% within minutes of their debut here on the New York Stock Exchange. Figuring out how to price the shares of social media companies is an incredibly difficult task. Most of these firms have little to no profits and relatively untested business models. This makes predicting their future profits - and thus, valuation in the form of share price - hard for underwriting banks such as Morgan Stanley and Goldman Sachs. Price shares too high, and you risk turning off investors. Price them too low, and you risk leaving money on the table and turning away long-term investors, who might dislike volatility. In general, tech companies tend to post bigger first-day jumps than the overall market. However, first-day "pops", as they're known, have become a common occurrence recently, as the first wave of social media companies go public. LinkedIn's shares surged 84% in their first few minutes of trading in 2011, online radio Pandora jumped 60%, and couponing site Groupon was up 34% when it debuted. But others started with a small boost before declining well below their opening price. That's what happened to Facebook, whose shares only beat their opening price this summer, more than a year after their debut. Twitter's surge means founders such as Jack Dorsey and Evan Williams missed out on a fair bit of cash. But it doesn't necessarily indicate anything about the future performance of the stock. That will depend on the company's first earnings report, which will be closely watched to see if the firm can translate its strong mobile presence into even stronger ad revenues.

When Facebook launched on the Nasdaq, its shares were priced initially at $38 each. The stock soared within hours of its debut to a high of $45. But its price later slumped.

It only recovered those losses by 11 September 2013, when shares again touched $45.

Its initial public offering (IPO) was also marred by technological glitches and delays.

To prevent Twitter's stock sale from having a similar fate, the NYSE ran tests on 26 October using larger-than-normal share volumes.

Financial scrutiny

Twitter is selling 70 million shares, which will raise more than $1.82bn.

The company, which invites users to send tweets in 140 characters or less, has 232 million active users. According to its IPO documents, these users send 500 million tweets a day.

Twitter's financials have been under greater scrutiny since it announced its plan to float, especially given that the company is still loss-making.

It lost $69m in the first six months of 2013 on revenues of $254m. About 85% of revenues come from advertising on its site, and more than 75% of Twitter users access the site from their mobile phone.

Mary Jo White, head of US regulator the Securities and Exchange Commission, recently warned investors to be cautious of the metrics used by technology companies such as Twitter, noting that investors have become overwhelmed by the sheer magnitude of data.

"In the absence of a clear description, it can be hard not to think that these big numbers will inevitably translate into big profits for the company," she said in a speech.

"But the connection may not necessarily be there."

Big windfall

Twitter's founders saw their paper wealth soar to $4bn in the wake of the stock surge early this morning, although boss Dick Costolo said that none of the founders would immediately be selling their shares.

The company's co-founder Evan Williams has a 10% stake in Twitter, making him its biggest shareholder. That stake is now worth a little over $2bn.

Jack Dorsey, another co-founder, also stands to make a fortune from the IPO. His 4% stake is worth more than $1bn.

Another co-founder, Biz Stone, is thought to have made millions of dollars by selling share stakes over the past few years.

Big fortunes aside, after the hoopla of the morning it was very quickly was back to work: Twitter employee Melissa Daimler posted a photo of employees at their desks just hours after the NYSE bell was rung.