SAN FRANCISCO, USA: U.S. Web search leader Google Inc said on Tuesday its employees exchanged about 93 percent of "underwater" stock options for new options with a lower exercise price.

The exchange, which became a subject of shareholder criticism after it was announced in January, was completed on Monday morning.

According to a regulatory filing, 15,642 Google employees participated in the program, which allowed employees to swap stock options with exercise prices above the stock's current market price for new options with an exercise price of $308.57 -- Google's Friday closing price.

Google's stock has fallen 49 percent from its 52-week high of $602.45. The company has said resetting the price of stock options is a way to motivate and retain employees.

Other companies, including Starbucks Corp, Advanced Micro Devices Inc and eBay Inc have also said they would exchange underwater employee options.

Google previously estimated it would take a $400 million charge to account for the exchange, assuming the new options were priced at $350 and that 100 percent of eligible options were exchanged.

The company did not provide a new estimate for the charge on Tuesday, but said an aggregate of 7,636,552 shares of Google's Class A common stock were exchanged, representing 92.3 percent of all eligible shares.