SP500 Droite CAGR Auto (bandes + label dynamique)

This indicator plots the long-term Compound Annual Growth Rate (CAGR) line of the S&P500 from a chosen start date (default: 1973).
It helps visualize whether the index is currently overvalued or undervalued compared to its historical growth trend.

Key Features:

CAGR Trendline (red): straight line connecting the start price (e.g. 1973 = 111.05 points) to today’s price based on compounded average growth.

Observed vs Fixed Mode:

Observed → CAGR automatically calculated from start date to the present.

Fixed → user-defined CAGR (e.g. 8.3%/year).

±20% and ±10% Bands (toggle on/off):

Provide tolerance zones around the long-term trend.

Useful to identify over/undervaluation ranges.

Customizable colors: for trendline and both bands.

Dynamic label (at the latest bar):

Displays the CAGR used (% per year).

Shows current deviation of the S&P500 from the CAGR line.

Gives a clear reading:

✅ “SP500 in the central band”

🟧 “SP500 between ±10% and ±20%”

🔴 “SP500 > +20% (overvalued)”

🟩 “SP500 < -20% (undervalued)”

Purpose:

This tool is designed for long-term investors. It helps to:

Spot periods of structural overvaluation (excessive bull markets).

Identify historical undervaluation phases (long-term opportunities).

Serve as an objective benchmark against short-term market noise.

⚠️ Tip: use the indicator with a logarithmic scale for correct visualization of compounded growth (the CAGR line appears straight on a log chart).