If one in ten thousand in the U.S. were to wear kilts regularly (and for argument's sake, let's say that was outside of pipe band activities), then a total of about 15,000 men in a country of 300 million persons would be wearing a kilt regularly(more than once a month). That "one in 10,000" is based solely on my local observations, in an area with about 40,000 population. Although, it seems as though there's rising tide of interest amongst certain sectors, so I can only imagine those numbers will increase.