Pinterest, the fast-growing, highly valued Visual Web startup, is far ahead of the Silicon Valley pack when it comes to gender diversity. But it's vowing to do far better on both gender and racial diversity, cofounder Evan Sharp promised in a blog post on Thursday.Startlingly, despite Pinterest's efforts to improve its numbers, its industry-leading ratio of women tech employees stayed steady at 21 percent from 2014 to 2015.See also: Why Pinterest's Workforce Is The Future Of TechThat's nearly twice the ratios other large tech companies have reported.