Diversification Logic¶

Why It Matters¶

Naive resource allocation either over-concentrates (putting all effort into the "best" option) or equally weights everything (treating all options as equivalent). Both fail. Diversification resolves the apparent paradox that you can simultaneously believe something is your best option and still allocate only part of your resources to it. It corrects the systematic error of confusing "highest expected value" with "optimal allocation."

The Key Move¶

For any collection of options, ask: what are the correlations between them? Identify options that tend to succeed or fail together (high correlation) versus those that move independently or inversely (low correlation). Preferentially combine low-correlation options. Calculate whether adding a mediocre option with low correlation to your existing allocation improves the overall risk-return profile.

Classic Application¶

Stock portfolio construction. A portfolio of 30 randomly selected stocks has about 70% lower volatility than a single stock, even though the average stock quality is unchanged. The risk reduction comes from imperfect correlations—when one stock drops, others may hold steady or rise.

Surprising Application¶

Skill development for career resilience. Building expertise in programming and public speaking (low correlation skills) provides more career stability than doubling down on two types of programming (high correlation). If the tech industry contracts, strong communication skills retain value in other fields. The person with varied skills has lower "career volatility" than someone with twice the depth in one domain.

Failure Modes¶

Assumes correlations remain stable—during crises, everything becomes correlated (the "correlation goes to one" problem). Doesn't work when sample size is small (you can't diversify across three job applications). Ignores concentration limits—you can't diversify your romantic partner. Breaks down when options aren't truly independent (apparent diversification in 2008: banks thought they'd diversified risk, but all mortgage-backed securities moved together).

Go Deeper¶

Bernstein, The Intelligent Asset Allocator, Chapter 2; Elton et al., Modern Portfolio Theory and Investment Analysis, Chapter 7