Facebook Inc. shares dropped as much as 3.9 percent to a record low Wednesday, the fourth straight day of declines after the world’s largest social-networking service reported second-quarter results that showed slowing growth.

The shares ended down 3.8 percent at $20.88 in New York, after earlier touching $20.87, the lowest intraday price since the Menlo Park, California-based company held an initial public offering on May 17.

Facebook, which hasn’t closed above the $38 IPO price since its first trading day, reported second-quarter sales growth of 32 percent, down from 45 percent in the previous three months. The company still needs to prove to investors that it can profit from the growing number of users who access the site on mobile devices, said Tom Forte, an analyst at Telsey Advisory Group in New York. He estimates that ads shown to handset users generated only about $15 million last quarter.

“The market has spoken,” Forte said. “They think that the price that investors are being asked to pay for a company in a state of transition when it comes to mobile monetization is too high.”

Second-quarter revenue was $1.18 billion, Facebook reported on July 26, topping an estimate of $1.16 billion, according to data compiled by Bloomberg. Facebook’s operating margin dropped from a year earlier and payments-related sales were $192 million, below the $199.3 million average projection.

Revenue may climb 30 percent to $6.41 billion next year, from $4.94 billion in 2012, according to the average analyst estimate compiled by Bloomberg.

“The investor reaction I think has been glass half-empty on mobile monetization, whereas we’re a believer in glass half- full because they are literally starting from nothing,” said Forte, who has a 12-month price estimate of $40 to $42 on the shares. “There oftentimes can be a disconnect between the market’s reaction on a stock and the underlying value.”