This calculator works out the number of years it will take for women to make up half the workforce at Google, Facebook and Apple. Just 31 percent of Google’s workforce is female, according to the latest published figures. At Facebook it’s 35 percent, and at Apple it’s 32 percent.

The first assumption is the share of new hires that is female, which kicks in over three years. The second assumption is the rate at which the workforce grows, which falls by 2 percent a year until it reaches zero. Finally, there is annual employee turnover. The calculator takes 20 percent turnover as its default setting.

You can also plug in the numbers for any company – including your own.

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