China’s previously overheated property market has been in the doldrums for most of this year but things are likely to get a lot worse, because of demographic shifts that are about to reverse a main driver of the decades-long boom.

According to newly published research, the size of China’s main property-buying population — people aged 25 to 49 — will peak next year and then start to decline, just as a huge glut of new apartments hits the market.

This demographic will shrink drastically from 2018, with the number of urban homebuying Chinese falling much faster than contemporaries from the countryside, who are far less likely to have the means to buy expensive apartments, according to Ai Jingwei, an expert on Chinese real estate and author of the research.