It doesn't seem like much to ask for—a 5 percent return. But theodds of making even that on traditional investmentsin the next 10 years are slim, according to a new report frominvestment advisory firm Research Affiliates.

The company looked at the default settings of 11retirement calculators, robo-advisers, and surveys of institutionalinvestors. Their average annualized long-term expected return?6.2 percent. After 1.6 percent was shaved off to allow for adecade of inflation, the number dropped to 4.6 percent,which was rounded up. Voilà.

So on average we all expect a 5 percent; the report tells us weshould start getting used to disappointment. To show how amainstream stock and bond portfolio would do underResearch Affiliates' 10-year model, the report looks at thetypical balanced portfolio of 60 percent stocks and 40 percentbonds. An example would be the $29.6 billion VanguardBalanced Index Fund (VBINX). For the decade ended Sept. 30,VBINX had an average annual performance of 6.6 percent,and that's before inflation. Over the next decade, according to thereport, “the ubiquitous 60/40 U.S. portfolio has a 0% probabilityof achieving a 5% or greater annualized real return.”