The subcontinent, as some people refer to India, is the 7th country by land mass in the world. It also has considerable variety in terms of its people. An indication of this can be gained by comparing how the various states shine in terms of national examinations. The answer seems to be: heterogeneous. States in India vary considerably.
What is interesting about this paper is that many of the usual explanations for group differences in intelligence don’t work in the case of India. Colder states are not brighter than warmer states, which is the usual pattern. Cities are not brighter than the country, which is the usual pattern. There is no relation with skin colour, ditto. To cap it all, states with good access to the sea, encouraging trade in goods and ideas are not brighter than the land-locked inland states.
India is mysterious in this regard.
For the quick summary, here is a Powerpoint presentation from the Graz conference which gives the key facts.
For more detail, here is the paper, which is also short, and discusses the findings, though without coming to any conclusion at this stage.
One probably needs to take into account the presence of clans, though categorising the exam results in this way might be very difficult:
In geopolitical terms the results strongly suggest that economic performance in India will show considerable variation from one part of the country to another. China may be more homogenous. Consult your own financial advisor before drawing any investment conclusions.