{
 "source": "Yahoo chart API ^GSPC daily closes, price only (no dividends)",
 "first": "1950-01-03",
 "last": "2026-09-18",
 "method": "share of start dates whose close N trading days later was higher (1 year = 252 trading days)",
 "periods": [
  {
   "label": "1 day",
   "trading_days": 1,
   "windows": 19299,
   "pct_higher": 53.1,
   "worst_pct": -20.5
  },
  {
   "label": "10 days",
   "trading_days": 10,
   "windows": 19290,
   "pct_higher": 59.1,
   "worst_pct": -31.5
  },
  {
   "label": "1 month",
   "trading_days": 21,
   "windows": 19279,
   "pct_higher": 61.8,
   "worst_pct": -33.0
  },
  {
   "label": "1 year",
   "trading_days": 252,
   "windows": 19048,
   "pct_higher": 74.6,
   "worst_pct": -48.8
  },
  {
   "label": "5 years",
   "trading_days": 1260,
   "windows": 18040,
   "pct_higher": 84.2,
   "worst_pct": -41.5
  },
  {
   "label": "10 years",
   "trading_days": 2520,
   "windows": 16780,
   "pct_higher": 93.1,
   "worst_pct": -44.9
  },
  {
   "label": "20 years",
   "trading_days": 5040,
   "windows": 14260,
   "pct_higher": 100.0,
   "worst_pct": 53.8
  }
 ]
}