Evan Spiegel just lost about $1 billion on Snap's first earnings report

Snap's first earnings report just took a big bite out of CEO Evan Spiegel's net worth.

Worth about $5 billion heading into the release, according to wealth rankings compiled by Bloomberg, Spiegel will see that slide to roughly $4 billion if Snap's 25% post-market stock slide continues into regular trading on Thursday.

Spiegel owns about 14% of the company's shares outstanding, making him the second-biggest shareholder, trailing only co-founder and chief technology officer Robert Murphy.

The swift negative reaction in Snap shares came after the company missed Wall Street profit expectations, while also reporting that user growth slowed to its lowest pace in years.

Snapchat's weak user growth comes as Facebook has intensified its mimicking of the Snapchat Stories format across its suite of apps. Instagram Stories recently outpaced Snapchat by reaching 200 million daily users.