How to estimate the number of taxis in Köln ?

Hi, I would estimate this way. I hope it helps. 

- (N° of residents * % residents no driving license * % residents no car * % residents no public transport) * N° drive over year  / AVG N° of passages each taxi

- N° of residents = 1M

- % residents no driving license = 1/2 (I am assuming 4 clusters of people (0-20years old; 21-40 years old; 41-60 years old and +61 years old) and I exclude 0-20 (too young) and +61 (too old))  

- % residents no car = 50% (I am assuming that in a normal family, like mine, we have 1 car every two people

- % residents prefer taxi than public transport = 50% (I am assuming two segments: the one who takes taxi and the one who takes public transport) 

- N° drive over year = 1 (1 drive each week) * 52 weeks = 52 (round to 50 for simplicity)

- THEREFORE, the upper part is = 1M * 0.5 * 0.5 * 0.5 * 50 = 6250K people (market demand)

- AVG N° of passages each taxi = AVG time each drive * AVG n° people each drive * Daily working hours * 310 (day in a year, 365 - 52 weeks (1 free day a week) = 312, but 310 for simplicity)  

- Daily working hours = 8 h 

- AVG time each drive = 20 min = 1/3 h 

- AVG n° people each drive = 2

- THEREFORE, the lower part equals to = 8 * 3 * 2 * 360 = 48 * 310 = 14880 (I will round it to 15K)

- THEREFORE, to serve 6250K potential customers, given that a single taxi can serve 15K of them daily) = 6250K / 15K = roughly 415 taxis

Number of residents(1M) * avg taxi rides per residents per month (1)= total demand of rides (1M)

avg. rides per taxi in one 8h shift (15)* 2 shifts per day * 30 days per month = total rides offererd (900)

1m/900 = 1111 or 1100 taxis in Cologne

[Pop Koln] * [% adult] * [% drivers license] * [% work] * [% work in transportation] * [% work in people transportation] * [% work for taxi company] * [1/# people operating under the same taxi]