There are statistics on % of the population (or households) that own guns, which might be what you're looking for? In your example that would be 50%, as one of

There are statistics on % of the population (or households) that own guns, which might be what you're looking for? In your example that would be 50%, as one of the people owns one-or-more guns, and the other owns zero. In the U.S. the ownership rate hovers around 30%, though it varies considerably by state, from a low of 9% (Hawaii) to a high of 60% (Wyoming).