The U.S. and Canadian defined contribution systems are failing 401(k) retirement savers on a number of counts, including a lack of diversification and an overdependence on the "style box" investment design, warns a defined contribution industry report from Clear Path Analysis released Thursday.

The North American DC marketplace may be maturing, but its continued reliance on U.S. securities shows a lack of diversification that is harming investors, especially as the U.S. markets struggle against the current low-interest rate environment, concludes the "DC Retirement Plan, North America 2013" report from London-based Clear Path Analysis.

According to Robert G. Capone, executive vice president of BNY Mellon Retirement, who is quoted in the report, great disparities continue between investment opportunities and resulting performance of both DC and defined benefit (DB) plans—and the underlying asset class exposures "factor prominently" in the results.