Snapchat is primarily used in the US, Canada, etc. In the US, there are 23.8M children aged 12-17. If we average it out and assume that every year when a kid t

Snapchat is primarily used in the US, Canada, etc. In the US, there are 23.8M children aged 12-17. If we average it out and assume that every year when a kid turns 13 they start using Snapchat, that's only 4M users a year. Given their growth of users is higher per quarter than that, they very well could be growing from exactly this source. Just because they aren't growing at the same rate doesn't mean they aren't growing. In fact, if we expect the model you suggested, it seems that their growth rate will continue to slow as they accumulate more users but the birth rate of wealthy countries (primary users of Snapchat) stays at the levels expected. Even though the birth rate is increasing, I don't think it will as much as the percentage of users of Snapchat increases. https://www.childstats.gov/americaschildren/tables/pop1.asp https://www.childstats.gov/americaschildren/tables/pop1.asp