How many backyard bomb shelters were sold per year between 1950 and 1990?

In the US, bomb shelters were a boom in business in the late 1950's and early 1960's; the Eisenhower/Kennedy years. They were hardly spoken of after the mid 1960's. By the late 1960's people often spoke fun of those people (made fun of them) that built those bomb shelters. ALthough no doubt some may still exist, bomb shelters in the US are a thing of the past which ended in the 1960's.