Settlement size distributions
Steep and flat size distributions:
Flat = all the settlements are about the same
   size
Steep= there is one big settlements, no middle-
sized ones, and a lot of small ones. This is also
called “urban primacy”
The lognormal and rank-size distributions.
Rank-size: the second largest settlement is one
half as large as the largest settlement, the third
largest is one third as large, and so forth.