Correlation

Correlation measures how two assets move relative to each other, expressed as a coefficient between minus 1 and plus 1. A value of plus 1 means perfect lockstep, zero means no linear relationship, and minus 1 means perfectly opposite movement. Portfolio construction depends on combining assets with low mutual correlation to reduce overall volatility.

Why it matters

Correlation is the mathematical basis of diversification, the one benefit in investing that costs nothing to obtain. Two volatile assets that move independently produce a smoother portfolio than either alone. The catch is instability: correlations are measured from past data and shift with regimes, and they have a cruel habit of rising toward 1 in crises, exactly when diversification is needed most. Serious allocators therefore treat any single correlation number as a snapshot, not a property.

In the gold vs bitcoin debate

Gold's near-zero long-run correlation with equities is the statistical heart of its portfolio case, letting a small allocation damp drawdowns. Bitcoin's correlation profile is younger and less settled: it traded nearly independently of stocks for years, tracked technology shares closely through 2022, and has decoupled for stretches since. The correlation between gold and bitcoin themselves has generally been low, which quietly suggests the two assets are complements in a portfolio rather than the substitutes the debate assumes.