But by the mid-1990's, with professional investors hungry for higher-yielding investments, major Wall Street investment banks stepped up the volume of loan-backed bonds sold to pension funds and other institutions.

Many depositors responded by switching some savings to higher-yielding investments, he said.

Only a quarter of the respondents had higher-yielding investments - stocks, bonds, certificates of deposit, mutual funds or money-market funds.

The recent European currency crisis helped to provide a good lesson for yield-hungry American investors who have been shifting their cash out of money market funds into higher-yielding investments.

Higher interest rates in the United States increase the value of the dollar, as capital flows into higher-yielding dollar-denominated investments.

As the reserves continue to grow, the central bank is aiming to boost investment returns on its foreign-exchange holdings by making somewhat riskier but higher-yielding investments.

A rate cut would hurt the dollar by encouraging money managers to buy marks or yen as they seek higher-yielding investments abroad.

The securities at issue are not part of Fannie Mae's core mortgage portfolio but are part of a small group of higher-yielding investments by the company.

The changes are intended to give banks new sources of income and to encourage ordinary Japanese to move some of their savings into higher-yielding investments.

Bond markets around the world have been beneficiaries as frightened investors sold stocks and moved into higher-yielding investments.