Iowa employers were heavily represented on the lists of the nation's top insurers released Wednesday by the National Association of Insurance Commissioners, The Des Moines Register reported. Companies based in the state or with significant Iowa operations claimed six of the 25 spots on the annual list of the top annuities insurers, with ING U.S. leading the way at No. 6. It was followed by Sammons Financial Group, Aegon NV, Aviva USA, American Equity Investment Life Holding Co. and Principal Financial Group Inc.