Updated October 2026 · Mike Shell, Chief Investment Officer

Diversification is owning investments that don’t all move together, so the portfolio’s risk is less than the sum of its parts. It reduces the risk of any one holding. It doesn’t stop a decline when everything falls at once.

Hundreds of holdings can still be one bet.

Why it matters. Diversification is called the only free lunch in investing, but only while the parts stay different. Many portfolios called diversified hold several versions of one risk: stocks, real estate, high-yield bonds and private equity all need the economy to grow, and they tend to fall together when it stalls. What matters is how many different reasons a portfolio has to make money.

The math. If every holding has the same return, the same volatility and the same correlation ρ with the others, combining N of them raises return per unit of risk by 1 ÷ √(ρ + (1 − ρ) ÷ N). Ten uncorrelated holdings: 3.2 times. Ten holdings correlated at 0.6: 1.25 times, and at 0.6 no number of holdings gets past about 1.3. Ray Dalio calls the first case the Holy Grail: 15 to 20 good return streams that are uncorrelated. Returns add. Risk doesn’t.

How it’s applied in ASYMMETRY® Managed Portfolios. We diversify the sources of return, not the number of positions: trends in different markets, rotation toward what is strongest, positions designed to gain in a large decline. Diversification is one layer of the defense, not the whole of it. When correlations rise, each position’s predefined exit and size are there to limit what diversification can’t.

Common misconceptions. More holdings isn’t more diversification: many funds holding the same stocks is concentration with more paperwork. Diversification isn’t a hedge. It lowers the chance that one holding sinks the portfolio, not the size of a broad decline. And uncorrelated in calm years can turn correlated in one bad month. From October 2007 to March 2009, nearly every major market fell between 27% and 69%.

Related terms. Correlation: the number diversification depends on. When diversification fails: what happens in a crash. Return drivers, barbell strategy and alternative investments follow in the lexicon. Part of the ASYMMETRY® guide to asymmetric investing.

Mike Shell is the Founder and Chief Investment Officer of Shell Capital Management, LLC, and portfolio manager of ASYMMETRY® Managed Portfolios, with nearly three decades of live-market experience across multiple full market cycles.