Well of course its not what you asked because you are implying that older populations dont make a difference in the economic power of a country.
For China's economic system to work they need about 20 younger people to support 1 retired person so that person gets to eat.
They dont have a financial system sector or a high technology sector they have a lot of low wage and low profit margin workers.
Their working population is fleeing the country and aging out of the workforce though and its not being replaced.
Their plan to economically collapse other countries and expand into them isnt working either. The countries neighboring China's empire have resisted their invasions and economic coercion.
The best estimates range from 500 million to 1 billion.
But definitely not 1.4 billion.
And it's aging and dropping faster every year, soon there won't be enough workers to support the elders.