The below graph shows each country expressed as a percentage of world GDP, and begins 2000 years ago. It's interesting to watch as the various world powers formed and then receded right up until modern times.

As everyone knows, China's portion of world GDP is rising for now, and ours is receding. For me, being 25% of the entire world's GDP is about enough and that about where the U.S. is.

China will begin to recede again, I believe, and that recession will steepen when their one child (i.e. mostly male) population begins to reach the age where they are no longer productive. That will be about 30 years.

And check out Russia, which peaked in 1950. Russia has lost 6 million people in just the last 15 years. Their population is down to 142 million, the average Russian man lives to be 59, and the Russian death rate per 1000 population is about 15 as compared to the world at about 8.
The article is real look-out-China-is-coming journalist type stuff, which I obviously don't buy. Be careful about reading too much into the beginning date. Note that the first 1000 years only take up an inch or so..As much as the last eight years. But there was no real world economy 2000 years ago.