A simple all-in/all-out strategy: usually owns the S&P 500, sometimes buys the Nasdaq after a sharp drop, and moves to Treasury bills when stock market signals look weak.

This strategy checks the U.S. stock market every day and puts all the money in just one place at a time. 1) If the S&P 500 looks healthy compared with its long-term trend, it buys SPY (a fund that tracks the S&P 500). 2) If not, but the Nasdaq looks beaten down after a sharp drop, it buys QQQ (a fund focused on big tech-heavy stocks). 3) If neither of those is true, but the S&P 500 is still above its recent average price, it goes back to SPY. 4) Otherwise, it moves to BIL, a very short-term U.S. Treasury fund that acts a lot like cash.

Dynamic, rules-based strategy shifting among SPY, QQQ, and cash to ride trends and limit losses. Out-of-sample: ~22.5% annualized vs SPY ~20.9%, lower drawdown (16.0% vs 18.8%), with stronger Sharpe/Calmar.