2020 was a banner year for U.S. IPOs even amid a global pandemic and financial crisis. Momentum will continue into 2021, with the hotly anticipated debuts of Roblox and Affirm.

At that market cap, Roblox would trade at 14.3 times its estimated 2021 bookings and about 89 times its estimated 2021 operating cash flow. This is no doubt expensive.

Roblox reported a year-on-year increase in revenue, rising 140pc to $387m in its first quarter of 2021. Bookings (that is, revenue that is booked but not yet in hand) also saw significant annual ...