Yield-based Allocation to Stocks and Bonds

Can investors beat a traditional 60%-40% stocks-bonds portfolio by adjusting allocations based on the earnings yield of stocks and the current yield of government bonds? In his March 2024 paper entitled "A Yield-based Asset Ratio to Boost Minimum Investment Returns", Arthur Eschenlauer tests a strategy that allocates to the S&P 500 Index or 10-year U.S. Treasury notes (T-note) via a Yield-based Asset Ratio strategy (YBAR), specified as follows:

• Compute minimum and maximum stock allocations that vary with S&P 500 long-term past earnings yield and current nominal T-note yield. The earnings yield is average earnings over the past 10 years divided by stock index level.
• Buy the stock index incrementally to rise to the minimum allocation whenever the stock allocation falls below the minimum minus 6% (a margin of safety).
• Sell the stock index incrementally to fall to the maximum allocation whenever the stock allocation rises above the maximum allocation plus 6% (a margin of folly).
• Whenever the stock index is very high, apply a cap to the stock allocation (a margin of reversion). The margin of reversion reflects how the earnings yield stands relative to historical values.

YBAR testing assumes 6% minimum acceptable stock allocation, 85% maximum acceptable stock allocation, 25% maximum reversion hazard and monthly portfolio assessment. Using Robert Shiller’s data as proxies for S&P 500 Index levels and earnings and for T-note yields during 1911 through 2022, he finds that: