A simple all-in/all-out stock timing strategy: it holds either SPY or short-term Treasury bills, using short-term market extremes, recent volatility, and bond-vs-cash strength to decide when to be in stocks.

This strategy only chooses between two holdings: <b>SPY</b> (a fund tracking the S&P 500, so basically big U.S. stocks) and <b>BIL</b> (a very short-term Treasury-bill fund, used like a cash parking spot). It first checks whether the stock market has moved <i>too far too fast</i> over the last week. If stocks look unusually overheated, it moves to BIL. If stocks look unusually beaten down, it buys SPY, betting on a bounce. If neither extreme is present, it checks whether the market has been very jumpy lately. If volatility is high, it stays in BIL. If volatility is calm, it uses one more test: are broad U.S. bonds (BND) acting stronger than Treasury bills (BIL) over the last few months? If yes, it owns SPY; if not, it stays in BIL.

Out-of-sample edge: higher risk-adjusted returns and stronger downside protection than the S&P 500. Sharpe 1.66 vs 1.30; max drawdown 12.6% vs 18.8%; Calmar 1.41. A smart, dynamic SPY/bill strategy that keeps growth while slicing risk.