Brendan Eich's support for California's ban on gay marriage was rare for Silicon Valley.

Eich lasted less than two weeks as CEO of Mozilla, stepping down Thursday over a $1,000 donation to the campaign to approve Proposition 8, California's 2008 voter-approved constitutional amendment restricting marriage to heterosexual couples. Proposition 8 stood until last year, when the Supreme Court left in place a lower court ruling knocking it down.

(Related: Brendan Eich steps down as Mozilla CEO over past support for Proposition 8.)

According to an analysis at, a small percentage of Silicon Valley donors who weighed in on the campaign sided with Eich.

Eighty-three percent of the employee donations from eleven Silicon Valley companies gave money to the campaign working to derail Proposition 8.

“So Eich was in a 17 percent minority relative to the top companies in Silicon Valley,” Nate Silver wrote.

“However, there was quite a bit of variation from business to business,” he added. “At Intel, 60 percent of employee donations were in support of Proposition 8. By contrast, at Apple, 94 percent of employee donations were made in opposition to Proposition 8. The opposition was even higher at Google, where 96 percent of employee donations were against it, including $100,000 from co-founder Sergey Brin.”