Courteous cities

Spore Sprout travels a great deal on business.  Wherever he goes, whenever he can, Spore Sprout gets on the local subway train, as much for the close encounter with his host city as for the time saved.

These days trains in many cities in Asia have "courtesy seats" that nearby signs urge you to give up to fellow passengers who are pregnant, underage, elderly or generally infirm.  As he is on the whole curious, and often tired, Spore Sprout typically watches these seats closely.   He finds there are observable differences among the cities in terms of the frequency with which subway train passengers give up their "courtesy seats" to those who may need them more.  In decreasing order of courteousness based on this measure, the four cities below rank as follows:

Taipei  >  Beijing  >  Hong Kong  >  Singapore