Proposed changes to pension fund accounting in the US are likely to prompt a shift of investment away from equities and into bonds while speeding the demise of defined-benefit plans, according to investment experts.

The accounting changes under consideration by the Financial Accounting Standards Board would require defined-benefit funds, which hold about $4,000bn (€3,400bn, £2,340bn) in assets, to stop "smoothing" their returns and instead report actual returns each year.