What is the test for apportioning a person's vote based on where they live?

This approach is consistent with the general principles expressed in the following passage in Reynolds v. Sims (supra) at pages 530 to 531: "To the extent that a citizen's right to vote is debased, he is that much less a citizen. The fact that an individual lives here or there is not a legitimate reason for overweighting or diluting the efficacy of his vote. The complexions of societies and civilizations change, often with amazing rapidity. A nation once primarily rural in character becomes predominantly urban. Representation schemes once fair and equitable become archaic and outdated. But the basic principle of representative government remains, and must remain, unchanged -- the weight of a citizen's vote cannot be made to depend on where he lives. Population is, of necessity, the starting point for consideration and the controlling criterion for judgment in legislative apportionment controversies. A citizen, a qualified voter, is no more nor no less so because he lives in the city or on the farm." (footnotes omitted)