Where to get population and demographic information

[KuJaX]

Where do real estate agents for residential and commercial get their demographic statistics?

For example, if you look at a home the real estate agent can EASILY give you all of the demographics or how many people live within 1 mile radius, 2 mile, 5 mile, etc, median age, income, etc.

I am assuming that this information originally comes from the county, but is there a website or software that calculates this information (such as a tool from Zillow?)

 

[Crono]

http://quickfacts.census.gov/qfd/index.html

 

[KuJaX]

http://quickfacts.census.gov/qfd/index.html

How do they calculate based upon a radius (such as mile, 5 miles) of a specific location? I see state info, county info and city info on the census website but no tool where I can specify a location and then get radius informatoin around that location.

 

[Crono]

paid service:
http://www.demographicsnow.com/

free version:
http://www.freedemographics.com/

 

[KuJaX]

paid service:
http://www.demographicsnow.com/

free version:
http://www.freedemographics.com/

Very interesting... mind if I ask how you find that (like what did you search or did you already know about it)?