The rate of technological progress is one reason behind this differentiating economic landscape. Mismanagement, as shown by the example of Sub-Saharan Africa, is another factor. The present divide is too clear-cut to be politically bearable in the long run. China has unclear but deep weaknesses, among which are its closed economy, its lack of infrastructure and of freedom, the absence of democracy, and a huge degree of social inequalities, hence a strong potential for political unrest. India, which is conventionally viewed with pessimism, is likely to become Number 2, although still far behind the US, by the year 2020-2030.
Prices tend to differ widely from country to country, namely for services.
Present economies are predominantly post-industrial, hence service economies. The physical output needs to be weighted by indexes other than local prices. This limits the impact of price distortions. This means that the average African person has a standard of living ten times smaller than the average inhabitant of the Far East.