Besides Airbnb, Dropbox and Stripe, more than 50 YC companies are each worth more than $100 million.

True: as of about January 2017, a YC portfolio list or valuation records show more than 50 YC companies other than Airbnb, Dropbox and Stripe each valued at over $100 million. Mostly true: the count is just short of or near 50 (about 45-50), or valuations are slightly uncertain, while the claim broadly holds. Mixed: the count is clearly below 50 but still large (about 30-44). Mostly false: well under 50 (e.g. 15-29). False: fewer than about 15 such companies.

Set before the research began.

1. E1 A List of Y Combinator Companies | Y Combinator Y Combinator · 9 September 2016

   “Number of YC companies worth more than $100 million: 52”

E1 is a September 2016 Y Combinator list that gives 52 as the number of YC companies worth more than $100 million, about four months before the claim. The quote does not say whether Airbnb, Dropbox and Stripe are among the 52. If they are, the count without them is about 49, which falls in the criteria's 45-50 "mostly true" band. If they are not, the count is 52 and the claim would fully hold. The source is YC's own published list, and the quote refers to YC companies as 'our companies', so it is a record from the organisation the subject speaks for rather than a fully independent source.