During the twentieth century, social mobility increased slowly but steadily in all high-income countries, with educational achievement and occupational status depending less on family background and more on cognitive ability and other personal characteristics. As a result, the lower socioeconomic groups have not only shrunk in size, but have probably also become more homogeneous in terms of personal characteristics that increase the risk of health problems.
因此，尽管福利国家的局部失败有助于解释健康不平等性的持续存在，但我们必须在他处寻找其愈演愈烈的原因并扭转这一趋势。两个可能的原因可以从这一主题迅速增长的学术论文中一窥端倪：选择性向上的社会流动和行为变化的滞后扩散。在现实中，这两大因素都在起作用。