In January, China officially acknowledged that its population began to decline last year — roughly nine years earlier than Chinese demographers and the United Nations had projected.

The implications of this are hard to overstate. It means that all of China’s economic, foreign and defense policies are based on faulty demographic data.

For example, Chinese government economists have predicted that by 2049, China’s per capita gross domestic product will have reached half or even three-quarters that of the United States, while its overall GDP will have grown to twice or even three times that of its rival. But these forecasts assumed that China’s population would be four times that of the U.S. in 2049. The real figures tell a very different story. Assuming that China is lucky enough to stabilize its fertility rate at 1.1 children per woman, its population in 2049 will be just 2.9 times that of the U.S. and all its key indicators of demographic and economic vitality will be much worse.