Zipcar's Stock Market Shares Zoom Upward Day After Successful IPO

Zipcar stockholders sold more shares than expected during the initial public offering on Wednesday.

Today, during the membership-based car sharing company's first day on the stock market, shares of Zipcar have beaten expectations again, rising upward by as much as 66 percent, the Wall Street Journal reports.

Zipcar, which provides rental cars to paying members by the hour or by the day, currently has 560,000 members, affectionately known as "Zipsters." Based upon the 38.6 million outstanding Zipcar shares trading at $30 per share, Zipcar is currently estimated to be worth $1.2 billion.

The rental company sold 9.68 million shares at its initial public offering at $18 each, raising $174 million, WSJ notes, more than expected by stockholders, who estimated they would sell 8.3 million shares at $14 to $16 each.

The company, not profitable nor expecting to be this year, plans to use IPO money to pay down debts. Revenue, however, climbed by 42 percent in 2010 after growing by 24 percent in 2009, Reuters reports.

Zipsters aren't required to pay for car insurance or gasoline, which could raise costs for the company this year as oil prices continue to rise around the globe.