In Norway, it used to be that to become a by (closest Norwegian equivalent to a city), a locality had to have at least 2000 inhabitants and be declared a by by parliament. Since most members of parliament were completely unconcerned about whether any particular place was a by or not, very few were declared.
Parliament, in fact, found the whole thing so boring that they changed the rules. Now, if you want to call yourself a by, you pass your own danged resolution in the local assembly and - poof! - you’re a by. This has led to some truly odd places declaring themselves byer - the tiny, very far northern town of Hønningsvåg did, for instance, mostly to annoy their rival Hammerfest, which had been billing itself as The World’s Northernmost City for years. On the other hand, here in Bærum, the township to the west of Oslo, we have 100,000 people and no cities. If the whole township was counted as a city, we’d be the fifth most populous in the country.