On: Many people are getting rare cancers in a small Ge...

[hervature]

Probability of 1 town of 10^5 people having 4 people disease with 1 in 10^-6: (10^5 choose 4)x(10^-6)^4x(1-10^-6)^9996 ~= 3.77x10^-6

Assuming independence between diseases and towns (not a terrible assumption but definitely not true) we have:

2000x200x3.77x10^-6 ~= 1.5

Which agrees with your simulation [1].

[1] My slow brain and calculator took 2 minutes to calculate this ;)

EDIT: Changed asterisks to x to avoid formatting.

EDIT 2: Here are the numbers for all the cases you have:

0: 361934.8

1: 36913.8

2: 1809.5

3: 60.3

4: 1.5