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Taking the Census, With Cellphones
sciencehabit writes: If you want to figure out how many people live in a particular part of your country, you could spend years conducting home visits and mailing out questionnaires. But a new study describes a quicker way. Scientists have figured out how to map populations using cellphone records — an approach that doesn't just reveal who lives where, but also where they go every day. The researchers also compared their results to population density data gathered through remote sensing technologies, a widely-used method that relies on satellite imaging to gather detailed information on population settlement patterns and estimate population counts. They found that the two methods are comparable in accuracy when checked against actual survey-based census data, but estimates from mobile phone data can provide more timely information, down to the hours.
Head counts are only a small fraction of the information that is gathered in a typical census (I've worked on a number around the world). Although important to determine population shifts & regional distributions of people, the more detailed demographics are what statisticians will be going through for some time after. A full census will provide details on household & family make up, religion & minority groups, immigration. I think the posted article has a long way to go to reach a full solution.
The primary purpose of a census is to determine apportionment to a legislature, that is, how many people require representation in a given area. Voters tend to be the elderly who have plenty of time on their hands and an inclination to follow politics. Elderly voters are much less likely to own those dang new-fangled cell-phones than trendy teenage non-voters. By conducting a census by counting cellphones, you end up ignoring politically active voters and counting politically oblivious non-voters.