To understand why so many economists - 24 out of 27 - got it wrong in tipping the Reserve Bank would cut interest rates yesterday, you need to know a bit more about the forecasting business.

All Australia's big banks and investment houses employ a team of economists to advise their clients - that is, investors - on the likely path for the economy. The more helpful the advice, the more likely it is that investors will use the services of that bank.

Reserve Bank boss Glenn Stevens perplexed economists by leaving rates on hold yesterday.

These private-sector economists produce regular forecasts for clients about the probable direction of economic growth, inflation, the exchange rate and interest rates during the coming year. Such client notes often find their way into the inboxes of journalists, providing a handy source of quotable quotes.

The problem is, these economists are only human.