The crisis of 2008 showed the perils that can lurk in rapidly growing financial sectors. And few have grown faster in recent years than the business of fund management.

Assets under management have more than doubled in size over the past decade, and the industry now runs some $74tn of money around the globe, according to Boston Consulting Group. That is equivalent to nearly one year’s gross domestic product for the world, or roughly two-thirds the total assets of its banks.

Growth in itself is nothing to worry about. But the sector’s explosion has gone hand in hand with a shift into more illiquid assets. Over the past 30 years funds have been moving away from developed government bonds and equities to more hard-to-shift debt holdings.

A larger, less-liquid industry poses questions at a time of uncertainty in financial markets. Nervousness is growing about the impact on asset managers of prospective interest rate rises and the unwinding of quantitative easing. These jitters have been compounded by the decision of sovereign wealth funds to pull money from asset managers, linked at least in part to the fall in the price of oil. In the latest quarter they yanked some $19bn according to the data provider, eVestment.

Fund managers are not banks. The fact that they do not, at least in theory, bear credit or liquidity risk ought to make them more resilient in a crisis. The worry, however, lies in the undertakings they have made to investors.

Just as competition before the crisis forced banks to “dance” while the music was playing, it has also forced many asset managers to assure clients they can withdraw their investments quickly. While funds retain some liquid assets to meet sudden cash calls, these could be overwhelmed were there a sudden stampede to redeem.