Google, concerned by the recent departures of several top executives, has developed an algorithm to try to identify which employees are likely to quit, according to a report in the Wall Street Journal.

The Journal said the internet search and advertising giant had turned to mathematical formulas because it was "concerned a brain drain could hurt its long-term ability to compete."

The newspaper said Google examined data from employee reviews and promotion and pay histories to try to identify which of its 20,000 employees were most likely to leave the California-based company.

Laszlo Bock, who runs human resources for Google, told the Journal the algorithm helps the company "get inside people's heads even before they know they might leave."

The newspaper said Google officials were reluctant to share details of the formula, which is still being tested, but it had already identified employees "who felt underused, a key complaint among those who contemplate leaving."