Eight founders of the world’s leading unicorn startups are sitting on personal fortunes of $31 billion, according to the Bloomberg Billionaires Index. The true value of those fortunes in the public market will be tested if Snapchat parent Snap completes the initial public offering it has filed confidentially for this month.

Snap’s IPO is expected in March and the startup is seeking a target valuation of $20 to 25 billion, as much as a 40 percent premium to its value on the private market. If Snap can pull it off, the two partners would become the youngest people on the Bloomberg Billionaires Index with a combined net worth of about $8 billion. If investors don’t bite, about $31 billion of unicorn wealth held by eight co-founders of Snap (Airbnb, Spotify, and Uber) could crater.

A potentially daunting sign for the unicorns is this month’s downdraft for public technology companies. The  S&P 500 Information Technology Index has dipped 0.6 percent since Donald Trump was elected U.S. president on Nov. 8, amid speculation that his trade and immigration policies could lower future earnings. The Bloomberg U.S. Startups Barometer, which tracks the overall health of the business environment for private technology companies based in the U.S., is down 21 percent from its peak in June 2015.

Some unicorns struggle to hold onto their lofty price tags. Elizabeth Holmes, founder of Theranos, saw her $4.5 billion fortune vanish on the Bloomberg index in April after the blood-testing startup came under scrutiny by federal and state authorities in California. Home decor startup Fab.com had a $1 billion value in 2013 and sold for $15 million two years later after revenue shortfalls, job cuts and departures of key executives.