I have this issue frequently when doing market sizing. It is quite straight forward to narrow a problem down in terms of the B2C market (age, demographics, income ... etc.) and then arrive at a first market estimate (let's say for electric cars sold). However, I then struggle how to walk through a second branch, such as B2B. Is there a common rule of thumb of how many business there are per person? I would assume for 20 persons, there is at least one business. Then I would have to segment the businesses by industry which can get quite daunting.
What is the way to go here?