Evaluate S&P 500 seasonal windows before using leverage

A calendar procedure, not a finished strategy

The archive treated month-of-year as a single testable variable for entry, exit, and abstention. Seasonal-trading is a testable calendar procedure that maps the month of the year into entry, exit, or cash rules for a single market.

The resulting seasonal system was presented as an illustration rather than a complete standalone strategy. Seasonality-analysis is a comparison of average monthly returns and rise frequencies that places one equity exposure inside a multi-month market regime.

Monthly windows and holding-period risk

Over the 1950 to 1995 monthly S&P 500 close-to-close sample, the average month gained 0.74% and finished higher 57% of the time. Extending the same sample to 12-month holding periods raised the average gain to 9.0% and the rise frequency to 71%, illustrating how longer horizons lift the historical probability of a gain.

Holding-period risk is the chance of a long stretch with no recovery, which lengthening time in the market reduces only if the investor can stay fully funded.

December was the strongest and most frequent up month, averaging 1.77% and closing lower 24% of the time. November, January, April, and July were also above the 0.74% monthly average. September was the only month with a negative average return and closed lower 61% of the time. May, June, and September formed the weakest cluster.

Multi-month regimes and the cash alternative

November through January averaged 1.58% per month and rose 67% of the time. Adding February through April still left 1.19% per month and a 65% rise rate, versus 0.29% per month in May through October.

A calendar rule that is long only in November through April and in cash otherwise produced a much larger terminal value from the same 1950 starting stake than the reverse May through October long rule. Risk premium is the extra expected return demanded over a cash or Treasury-bill alternative before accepting equity risk.

Seasonal leverage-control versus constant margin

Buy-and-hold of the S&P 500 from January 1950, ignoring dividends, turned 10000 into 372388 by December 1995, with an 8.4% average, 14.4% standard deviation, and a 41.3% maximum loss.

Leverage-control is a pre-trade exposure bound that scales position size by seasonal window instead of applying constant margin. A three-state seasonal exposure rule, fully leveraged in the best six months, unlevered long in the next three, and in Treasury bills in the worst three, grew 10000 to 1839958. A worst-period loss near 50% would have required a 100% recovery to break even.

Constant 2-to-1 leverage every month from 1950 to 1995 produced only 54903 from 10000, with a 28.5% standard deviation and a 70.6% maximum 12-month loss. That result was worse than unlevered buy-and-hold and worse than Treasury bills on a risk-adjusted basis.