Selectivity of human migration long been the focus of demographers and economists.人口遷移的選擇性一直以來都是人口學(xué)家和經(jīng)濟學(xué)家關(guān)注的焦點.In the public's eyes , demographers have a checkered reputation.民眾對人口統(tǒng)計學(xué)者的評價不一.Demographers talk about a...