Fortunately, in epidemiology and economics it is not necessary to
have exact counts of population by political division. However, it is
useful to be able to estimate cases and deaths as well as where to
place laboratories, clinics and transport hubs. It is particularly
disappointing when, for example, the estimates of how many people live
in the city, local government area and metropolitan area of Lagos
differ substantially across the web pages maintained by the mayor's
office, the next higher political division and the national
government. None of these six measures agree with the CIA World
Factbook, www.citypopulation.de or other sources. In a sense,
sometimes it is enough to say that Lagos has more than 10 million
people and likely less than 20 million people. But, since building
clinics and labs takes time (and people suffer and die during that
time), surely it is important to be able to count to the nearest
100,000 or even one million people. That should not be taken to mean
that cities with 100,000 people and no significant metropolitan area
should not have accurate counts.