China at 0.97 fertility. The US at 1.6 plus a million legal immigrants a year plus the unauthorized flow. The headline gap is demographic, the structural gap is selection.

Beijing imports zero. Washington runs an H1B funnel that absorbs the global top of the distribution. Founders, doctoral researchers, the capital that compounds technological frontiers. Population maintained on one side, talent concentrated on the same side. Two levers pulling the same direction.

The rivalry of the next two decades still gets played with China at full scale. After that the asymmetry hardens. By 2100 the ratio is under two to one, with the American talent stack having compounded through four more cycles of selection.

China cannot reverse course. The clock runs in one direction.