ST. LOUIS--(BUSINESS WIRE)--A majority of investors have taken advantage of low interest rates, according to the third quarter Wells Fargo/Gallup Investor and Retirement Optimism Index survey. The survey of 1,006 U.S. investors was conducted August 7-16; the median age of the retired investors is 70 and the non-retired is 45. Six in 10 investors (58%) are benefiting from lower rates either by taking out a car loan (30%), refinancing an existing mortgage or home finance loan (17%), taking out a