These billion-dollar startups more than doubled their value in 2015

There are more than 145 companies worth more than a billion dollars in Silicon Valley.

Of those, 21 more than doubled their value in the last year.

Venture capital database CB Insights tracked the list of the biggest unicorn valuation increases of the year. (Unicorn is Valley parlance for a company worth more than a billion dollars).

Here's the list of companies that more than doubled their value in the past year, courtesy of CB Insights: