Volatility Drag & Compounding Returns
When looking at stock market index returns or private portfolio statistics, financial institutions often cite arithmetic averages. However, because money compounds, the path of your investment matters. Geometric returns calculate the true growth rate, showing the smooth compound rate required to achieve the final balance.
Comparing Return Types
Arithmetic Average
Calculated as a simple sum divided by count. Useful for projecting a single period's expected return but ignores compounding sequences.
Geometric Compound Return
Accounts for compounding by multiplying the growth factors of each period and taking the n-th root. This is the CAGR of the asset.
Volatility Drag
The difference between the arithmetic and geometric averages. High asset volatility decreases actual compound growth relative to the simple average.