How would you estimate number of cars in a perticular city?

Question

Any intelligent people here who can help me with estimation problems? What is exact approach in solving these questions? mind you i am not asking for a figure of number of cars but how to approach the problem? it could be "hou would u estimate cafes in a city" or petrol pumps? etc etc help needed urgently...!!!

Answer 1

There are two ways of doing quantitative estimates to problems like "how many bricks in the Great Wall" or "how many tennis balls in the United States?". In this case, let's use cars in a particular city.

1. Top-down. Take the population of the city. Countries and/or states often have car ownership records, whoever is the registration authority. In the US, you would use the State DMV, but the US Dept. of Transportation also has that. You would then apply a ratio to the population of the city. You would then adjust the resulting number by demographics. Compare the cities demographics compared to the "average city" in the city/state. For example, cities tend to have younger, richer population. There may be other factors like the antiquated road infrastructure (e.g. Rome), extremely high cost of living/car ownership (e.g. New York City) or car taxes (e.g. Singapore).

2. Bottoms-up. Sometimes you can collect the data manually. Usually, this type of estimate works only were data integrity is good and available. Also, you usually have to do a reality check against a top-down guesstimate anyways.