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Facts
China's GDP is almost 5 Trillion,
India's GDP is about 2 Trillion.
The USA GDP 14 Trillion.
Ours still doubles theirs combined. And we have 1/8th the Population that have combined.
That's nominal GDP, it's only relevant for India, as India still imports a lot of stuff and service from abroad, which it can't produce as it lacks the technological skill for it. China is different as it is a self-sufficient industrial power. What China imports from abroad is not a neccessity, but concessions to trade-partners and easing of the trade imbalance.
With China you have to look at GDP purchasing power as from Frigates to Computers is all produced within China.
Nominal GDP only becomes relevant when you buy or import things from a different currency-zone.
China's GDP-PPP is 9 Trillion $. It grows every year by +/- 10%. It adds every year at least 900 Billion $ to its economic output.