And if we assume that you are 40 years old (don't correct me if I'm wrong), and have been buying yearly since your 20s, that's a factor of 20 to account for duplicate owners (well, you may be their best customer, so that's an upper bound on the factor).
And if we assume that you are 40 years old (don't correct me if I'm wrong), and have been buying yearly since your 20s, that's a factor of 20 to account for duplicate owners (well, you may be their best customer, so that's an upper bound on the factor).