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Estimationwarm-up
How many smartphones are sold in the US each year?
How to approach it
Use a replacement-cycle approach: people who own smartphones divided by how many years they keep one.
How a strong answer opens
“I'll use a replacement cycle: smartphone owners divided by how many years people keep a phone, plus first-time buyers.”
Outline of a strong answer
Try answering out loud for a few minutes before you open this.
- State population, about 335 million
- Share who own a smartphone
- Average years before replacing a phone
- Owners divided by replacement years
- Add first-time buyers and second phones
- Sanity-check against carrier stores: stores x phones sold per store per day
Where this question usually goes wrong
Assuming everyone buys a new phone every year, which ignores the multi-year replacement cycle and inflates the answer.
Learn the method
The approach in five steps in Module 3, Estimation.
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