Rob Kapito, co-founder of $10 trillion investment giant BlackRock, says a global shortage of investable assets will help the sharemarket grind higher over the long term as dips in equity and bond markets are quickly met by investors hungry for returns.

Mr Kapito, who has day-to-day oversight of the world’s largest investment manager, said investors are sitting on a staggering $US50 trillion ($73 trillion) in cash - but are struggling to put it to work.