Imagine an equity market in which 98 per cent of all shares are held in passive, index-tracking portfolios and only 2 per cent are actively managed. In such a market, active management of the 2 per cent will determine share prices for the remaining 98 per cent.

Merely an interesting theoretical observation? Look more closely at the structure emerging in today's equity markets. We are moving towards a highly polarised structure in which the behaviour of the few is shaping markets for the many.