Colons are commonly used to introduce lists, or to connect a broad idea with a specific example: two related sentences can be separated by colons instead of periods.
... household size is 2.57 and the average family size is 3.08.
In the town the population is spread out with 22.3% under the age of 18, 6.3% from 18 to 24, 31.0% from 25 to ...