Investors in 401(k) plans didn't do a lot of trading within their accounts in September, according to the latest 401(k) Index by Aon Hewitt.

Daily transfer volumes averaged 0.026 percent of balance totals per trading day in September, just slightly below the 12-month average. There were only three days that experienced above-normal levels of trading.

According to Aon, a September statement by the Federal Reserve stating that it would not begin tapering its monthly bond-buying program had a positive impact on the equity and bond markets. The S&P 500 returned 5.2 percent during the period and non-U.S. equity indices also posted positive results. The fixed-income markets experienced rising yields for most of the third quarter, but the Fed's announcement provided a boost as prices rallied and yields declined, helping to bring the fixed-income markets into positive territory for the third quarter, the company found.