Things are getting crowded in the once-exclusive unicorn club...
This is all still-private unicorns since 2011 and charted them based on when they first joined the unicorn club.
[2]
(click image for large legible version)
While initially the chart shows unicorns being created at a relatively calm pace, the rhythm accelerates noticeably in late 2013 (right around the time Aileen Lee wrote her famous post coining the term unicorn in November 2013 [3]). Since then, there has been an explosion in unicorn creation, with over 60 new unicorns in 2015 alone.
Source: CB Insights [4] via Valuewalk.com [5]