The data to resolve this market will be pulled from https://ourworldindata.org/grapher/population?time=2000..latest (or some other source if this one becomes unavailable).

If the world population in year N is more than the world population in year N+1, this resolves to the population in year N.

If this never happens (population grows throughout the 21st century), this resolves to the population in year 2100.