system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Where did the age requirement of 21 come from as opposed to 20 (or any other number above 18) in order to legally drink?

What caused it to be set at precisely 21?
gpt
In Sweden you can drink alcohol when you're 18, but you need to be 20 to buy it over the counter.

The reasoning is that people who are 18 are still in high school and are therefore likely to have good contact with people as young as 16 who then would have easy access to alcohol. Where as if you're 20 you typically don't hang out with 16-17 year olds to the same extent.