3QUESTION 3 OF 3
Answer & explanation
The official answer, with Fermi’s reasoning step by step.
Answer & explanation
Official answer
140,000,000
bookcases
How to estimate it
Fermi’s official “Napkin math”
Oh boy, let's try and get close. I don't have a good feel for how many are sold each year, so let's start with homes. 8B people makes 2B homes, assuming 4 people to a home. How many homes have ever had a BILLY bookcase since 1979? I'd say at least 1 in 20.
- People on Earth
- 8,000,000,000
- About 4 to a home
- ≈ 2 billion homes
- 1 in 20 homes
- ≈ 100 million
Rounded assumptions may give a slightly different estimate. The official answer above is the game’s reference value.
Source calculation & reference
- Sold by May 2022 (IKEA newsroom)
- more than 120 million
- One sold every 5 seconds (IKEA) for 2.6 more years
- + 16 million
- Sold by December 2024 (Ingka Group, IKEA Retail)
- over 140 million
Reference cited by Fermi: IKEA Retail (Ingka), Dec 2024
How close was your guess?
Your comparison will appear here.
Compare by ratio: divide the larger number by the smaller one. The closer to 1×, the better.