Concerned a brain drain could hurt its long-term ability to compete, Google is tackling the problem with its typical tool: an algorithm. The Internet search giant recently began crunching data from employee reviews and promotion and pay histories in a mathematical formula Google says can identify which of its 20,000 employees are most likely to quit. Google officials are reluctant to share details of the formula, which is still being tested. The inputs include information from surveys and peer reviews, and Google says the algorithm already has identified employees who felt underused, a key complaint among those who contemplate leaving, reports Wall Street Journal.