Good as it was overall, 100-or-0 Rotation exhibited at least one consistent vulnerability. For the worst-month metric, it always finished in third place, better by far than stocks, but outdone both by bonds and by rebalancing. There's a simple explanation, and it has a clear message. If a strategy is 100% invested in stocks when stocks fall suddenly and dramatically in a very short period, as on Black Monday in October 1987 and in the flash-crash of 2010, then the portfolio gets the full effect. However, a portfolio invested partly or completely in Treasuries will partly or completely escape the damage. Furthermore, Treasuries will very likely rise in value at such times.
The natural question to ask is whether a better rotation would stay below some ceiling, never going to 100% in stocks. A related question might be whether 0% is, in fact, the best floor. Happily, the data of the last 100 years in U.S. markets and the last 25 internationally have clear answers for both questions. Next week's posts will show how the answers are derived.