Developer earnings are costs related to developers’ and creators’ accumulation of earned Robux and the subsequent exchange of those Robux for real-world currency. We intend to use future cost efficiencies earned in other areas of our business to increase earnings for our developers and creators thereby increasing developer earnings over time. For the nine months ended September 30, 2019, developer earnings were $70.9 million, or 15% of bookings, and grew by 190% to $205.4 million, or
17% of bookings, in the nine months ended September 30, 2020.
For Roblox, a "booking" is simply a sale that gets recognized over the lifetime of an average user.