I was not aware of any apportionment from the census except for determining the number of Representatives in Congress, but I'm willing to learn. Do you have a source I can reference?
Sometimes for a quick~n~dirty confirmation I’ll use wackypedia but I’m sure you would like something a bit more credible than them ;’)
Here’s one brief source:
http://constitution.laws.com/three-fifths-compromise
And here is a better one:
http://www.heritage.org/constitution#!/articles/1/essays/6/three-fifths-clause