A famous 1960s model, the Capital Asset Pricing Model, argued that a holding’s expected reward rises with its beta — its exposure to market-wide risk you can’t diversify away.[1,2]
Beta is how a boat reacts to waves. A heavy ferry barely rocks; a dinghy leaps with every swell — same sea, bigger motion.
Some risk is unique to one company and can be diversified away. Beta is the leftover, market-wide risk that diversification can’t remove — so that’s the risk you get paid for.
The real world is messier than the model: beta isn’t stable, and high-beta bets don’t always pay off. But beta is still a handy gauge of how much a holding rides the market.
Finisdom estimates beta from real price history, so you can see which holdings amplify the market and which cushion it.