Several questions rolled into one, I think.

Percentage of the male population owning a kilt: Scotland
Percentage of the male population wearing the kilt: Scotland
Number of kilts owned per male: elsewhere.

A large percentage of adult males in Scotland own a kilt, but almost 100 percent of males regardless of age will hire a kilt -- if they don't own one -- several times in their lives for weddings and other events. The comfort level with kilt-wearing is very high.

As has been said elsewhere, Scottish males who have a kilt have A kilt; rarely do they own or wear more than one. If they have a clan or family connection, that's the tartan they wear.