thanks to the baby boom in the 1950s and the implementation of the one-child policy beginning in the mid-1970s, China has enjoyed a huge demographic dividend beginning around 1970 or so, when people of working age comprised around 51% of the working population (one worker for every non-worker), to 2015, when they will comprise around 65% of the total population (one and one-half workers for every non-worker).  Their share is then expected to decline to around 56% of the population by the middle of the century. 

this has important implications both for nominal growth rates and per capita growth rates in the next few decades.

beginning some time in the next decade, China’s working population will begin to grow more slowly (or shrink more quickly) than its total population, suggesting that the demographic dividend it has enjoyed during the past three decades will become a demographic tax.  Per capita income, in other words, will grow more slowly than the growth in worker productivity.