Exactly 100 million pi (roughly)
The US Census Bureau estimates that the population of the United States reached π×100 million on Tuesday afternoon (US time): 314,159,265. (via Stuff)
There’s no margin of error with this estimate, which might seem surprising from a respected national statistics agency. The reason is that there is no sampling error in the estimate, all the uncertainty is from non-sampling errors. The Census Bureau started with the 2010 US Census counts, subtracted deaths and emigrations (me, for example) and added births and immigrations. In principle, the data on all these is complete and no sampling is used. That doesn’t mean there isn’t any error — far from it — but it does make it very hard to estimate how much error there is.
The ubiquity of non-sampling error, and the impossibility of estimating it accurately, explain why surveys in New Zealand are about the same size as surveys in the USA, despite the huge difference in population. In theory, you could afford to collect larger samples in the US, so US statistical agencies could get more precise estimates than Stats New Zealand can afford. In practice, once surveys get to a certain size, the non-sampling error starts to be more important than the sampling error, and extra sample size stops giving you much increase in accuracy.
Thomas Lumley (@tslumley) is Professor of Biostatistics at the University of Auckland. His research interests include semiparametric models, survey sampling, statistical computing, foundations of statistics, and whatever methodological problems his medical collaborators come up with. He also blogs at Biased and Inefficient See all posts by Thomas Lumley »