Investors appear to be getting lower returns for accepting risk than they were 5 years ago, and that might be a sign that average returns will be substantially lower over the next 10 years.

Adrian Cronje, an economist at Wilmington Trust Corp., Wilmington, Del., a wealth management firm, has given that assessment in a discussion of the 10-year outlook for world capital markets.

“There are no more obvious bargains available,” Cronje says in the report, which was released today shortly before U.S. stock market indices began to plummet.

World economic growth may be robust in the coming decade, and prices are more likely to inflate than to deflate, Cronje predicts.

Cronje says risks that could throw off that forecast include a decline in U.S. labor force participation and productivity; a dollar currency crisis; the return of trade barriers and punitive tax policies; and a major terrorist action.

“The low risk premiums in today’s markets imply that many things are expected to go well, when they may not,” Cronje says. “Diversification and a long-term view will be investors’ best allies, as they always have been.”

Investors can use bonds and other fixed-income holdings to guard against unexpectedly low economic growth, and they can use inflation-linked bonds, real estate and commodities to guard against inflation, Cronje says.