UPDATE 1-Shares of online retailer Zulily soar 88 pct in debut
* Shares open at $39, above IPO price of $22
* Stock hits $41.32, valuing co at $5.04 bln
(Add details, analyst quote, background; updates stock move)
Nov 15 (Reuters) - Shares of Zulily Inc, which runs a website that offers huge daily discounts on clothing, soared 88 percent in their debut, valuing the company at about $5.04 billion, as investors bet on niche businesses.
The company's debut comes in a year that has seen the strongest market for U.S. IPOs since 2007, as equity markets soared, helped by economic growth and the Federal Reserve's efforts to keep interest rates low.
About seven companies have doubled in value on their first day of trading this year, with many more enjoying sizeable "first-day pops".
Seattle-based Zulily's shares opened at $39 and rose to $41.32 on the Nasdaq on Friday, after its initial public offering was priced at $22 per share, way above the expected range.
"The sector is strong and this is the star in the sector," said John Fitzgibbon, founder of IPO-tracking website Iposcoop.com.
Flash sales companies such as Zulily sell heavily-discounted merchandise in as many as 50-60 online sales events each day.
The sector grew quickly after the 2008 financial crisis, but not all companies have thrived more recently.
Amazon.com Inc, the world's largest online retailer, has its own flash sales business called MYHABIT, and investors are generally wary of putting their money in other e-commerce companies because of Amazon's dominance.
However, Zulily's focus on selling women and children's clothing and accessories has helped it grow quickly. Founded in 2009, the company said it currently has 2.6 million active customers.
The North American online retail market is expected to grow about 14.5 percent to $360 billion between 2012-2017, according to Euromonitor, a consumer market research company.
Zulily's revenue jumped to $331.2 million in 2012 from $18.4 million in 2010, but its net loss widened to $46.8 million from $7.4 million in the same period.
The company has almost tripled its workforce to 950 employees in the last two years.
Founders Darrell Cavens, who is the company's chief executive, and Mark Vadon, who heads online diamond and jewelry retailer Blue Nile Inc, together own more than half of Zulily's shares.
The company sold 6.4 million of the 11.5 million class A shares offered, while the rest came from selling stockholders.
The Seattle-based company raised $253 million in the IPO.
Goldman Sachs was the lead underwriter of the offering.
(Reporting by Neha Dimri in Bangalore; Editing by Don Sebastian and Savio D'Souza)