Currently on 40th birthday of first Index Fund, i.e. Aug 31, 2016 there are around 88 Index Funds and ETFs with asset size of around 30,000 Crores in India & steadily growing. (passivefunds.in)
This is because early academic research focused on market capitalization, although it's curious that the very first index fund in 1971 (Wells Fargo) was actually equal weighted. (business.financialpost.com)
In India first Index Fund was launched in 1999. (passivefunds.in)