Creators of proprietary indices can find an infinite number of rulesets that will show higher risk-adjusted returns based on historical data - but showing outperformance is not enough, there has to be a simple and intuitive reason for why the strategy outperforms that can persist into the future and cover the fees embedded in the index. That's a pretty high bar. But a simpler approach, a blended index that blends common equity and fixed income indices, has also been employed at some insurers because it shows extremely well in back-testing and delivers eye-popping participation.