“This is obviously because fixed income instruments are not as readily assessable to SMSFs as other assets are,” Credit Suisse said.

Credit Suisse added that it has been suggested cash is high yielding enough to replace bonds in an Australian portfolio.

“[However] we think cash is a poor replacement for bonds. Bond returns are usually negatively correlated with equities which help balance portfolio returns, especially during brutal equity bear markets,” it said.

“An allocation of 50 per cent Aussie equities and 50 per cent 10-year Aussie government bonds has lost money in only three of the past 34 years.”

Credit Suisse said that meanwhile cash tends to have a zero, or even a small positive correlation with equities, so it does not provide the same “portfolio relief” during stock market sell-offs.

“As retirement age looms closer we imagine SMSFs would not want their portfolios overly exposed to a single asset, our concern is that important investment lessons like this are often learnt too late,” Credit Suisse said.