Robert Elz <kre@munnari.oz.au> writes:

Having a simple rule that always gets followed allows us to ignore endless arguments

Yes, that's one of the principal motivations.

Of course, if it is a close thing, and it is possible that Shanghai may overtake Beijing again next year (or something) then keeping switching backwards and forwards would be irrational

Yes, in the past when this has happened, we've tried to avoid change for the sake of tracking the current ephemeral champion. Of course this has to be done within reason; if the new champion is undisputed then it would be time to change. But as far as Beijing vs Shanghai goes, it seems that the current headcount leader is still Shanghai, if we include the floating population and use the statistics James Su mentioned. Also, if we count the entire metropolitan-area population, the statistics I've seen suggest that Beijing still trails well behind Shanghai. See <http://www.citypopulation.de/World.html>, for example, which gives 12.1 million for Beijing and 18.2 million for Shanghai. Or <http://www.world-gazetteer.com/wg.php?men=gcis&dat=32&geo=-54&srt=pnan&col=a...>, which gives 11.5 million for Beijing and 14.9 million for Shanghai.