A revolution is shaking the world of indices as providers use different stock rankings to win business from clients increasingly sensitive to cost. The price war is fiercest between providers of commoditised cap-weighted indices, which underpin the vast majority of exchange-traded funds.

It was heightened last October when Vanguard, the world's largest mutual fund company, with $2.2 trillion invested in passive and active funds terminated MSCI, one of the world's largest providers of indices, as an index provider to passive funds and ETFs worth $540bn. Vanguard said it wanted to cut costs.