Jed Kolko, the former Under Secretary of Commerce for Economic Affairs of the United States, discusses the challenges of estimation and recent immigration numbers from the Census Bureau:
Numerous government agencies estimate the population. Annual Census population estimates guide the allocation of federal spending and also serve as the “population controls” for essential demographic surveys. (This turns out to be a big deal. More on this, below.) These annual estimates help bridge the gap between full-count decennial censuses, and they are revised to reflect new information each year. Other agencies produce population estimates and projections for their own purposes — CBO estimates and forecasts the population as inputs into their outlook for federal spending, revenue, and deficits.
Immigration is an essential part of estimating the size and growth of the population, and the trickiest.
