(added on 2008/11/07)
Distorted pyramid 變形金字塔
A population pyramid is a graphical illustration of the age distribution of a population. The shape of the population pyramid varies with birth rate, death rate and mobility as a result of migration. The population pyramid of Hong Kong does not fit into any standard shape. The group tip reflects an increase in elderly population while a contracted base is contributed by a low birth rate. Health correlation and mobility patterns have also shaped the pyramid, with slight variation across districts.