The Question: Please estimate how many checking accounts there are in the United States?
Potential clarifying questions: Which checking accounts – Personal? Business/Institution? Both?
For the purposes of this case let’s assume both.
Approach: Assume 300 million people in the U.S.
80% or 240 million are over the age of 18
Let’s make an assumption that all married couples have only a joint account and 50% of those over 18 are married
Let’s make an assumption that every single person over 18 has one account and no one under 18 does
Let’s assume that 60% of the population is in the workforce.
30% of those in the workforce are self-employed and 70% are employed by a firm.
Let’s further assume that the average firm (excluding those that are self-employed) has 10 workers, there is only one account per firm and those who are self-employed have one business account as well
So now your approach has been constructed with various sets of assumptions and you are ready to run through the numbers:
Personal accounts: 240 million people over 18
50% are unmarried and have one account = 120 million accounts
50% are married and share one account = 60 million accounts
Business Self-Employed: 180 million people are in the workforce, of which, 30% are self-employed = 54 million accounts
Business Employed by Firm: 180 million people are in the workforce, of which 70% are employed by firm with an average of 10 people per firm = 126 million divided by 10 people per firm = 12.6 million accounts
Conclusion: Therefore our approach yields an estimate of ~ 250 million checking accounts in the U.S.
