Bollinger Band Reversion for US500 (S&P 500)

Buy lower band, exit upper band — volatility-adaptive mean reversion.

Why Bollinger Band Reversion Works on US500

Bollinger Bands plot two standard deviations around a 20-period SMA. Price reaching the lower band signals a statistical extreme — about 2.5% probability assuming normality. The strategy fades these extremes. Works on range-bound symbols; layer in a "no entry if bands are widening" rule to skip breakout regimes.

The S&P 500 (US500) is the global benchmark equity index. Strong long-term uptrend with regime shifts; momentum and trend bots dominate, mean-reversion works in QE periods only.

Equity indices reflect aggregate corporate earnings, sentiment, and Fed policy. They trend more cleanly than individual stocks and gap less than commodities.

Pine Script Source

Copy this into PineForge — backtest on US500 or any supported symbol, then deploy as a live bot.

//@version=5
strategy("Bollinger Band Reversion", overlay=true)

length = input.int(20, "BB Length")
mult = input.float(2.0, "BB Multiplier")

basis = ta.sma(close, length)
dev = ta.stdev(close, length) * mult
upper = basis + dev
lower = basis - dev

if close < lower
    strategy.entry("Long", strategy.long)

if close > upper
    strategy.close("Long")