# Size Vs Junk

_Systematic Investing . 2026-07-02 . By Tanmay Kurtkoti. Educational, illustrative, not advice._

A friend runs a small-cap SIP and asked me last week whether the small-cap premium is real or just a story funds tell to sell the product.

Fair question. So I pulled the data. Ninety years of US stock returns. And here is the uncomfortable part. On its own, small beating large is marginal at best. Weak record, faded after everyone discovered it in the 1980s, mostly showed up in January and in microcaps you can barely trade.

Then I reread the Asness paper that reframed the whole debate. Size Matters, If You Control Your Junk.

Their finding is the kind that reorganizes how you see the problem. Small-cap universes are stuffed with low-quality companies. Unprofitable, indebted, fragile. Large-cap universes lean the other way, toward the profitable and stable. So the size effect was quietly fighting a quality headwind the entire time.

Here is the part that stops you. Among quality stocks, small beats large. Among junk stocks, small beats large. Small wins in both. But because most small caps are junk, the blended small-cap average still trails large. Small won every matchup and lost the scoreboard. A textbook composition trap.

Strip the junk out and the premium roughly doubles. It steadies across decades, shows up in 30 industries and 24 international markets, and stands on par with value and momentum.

So the honest version is not small caps are great, or small caps are a trap. It is that you want small AND good. And you cannot eyeball junk out of a 500-name universe by hand. A rule that screens on quality does it every rebalance, without your mood getting a vote.

Small caps were never the free lunch. They were never the trap either. The junk inside them was.

How a rules based basket screens the junk out instead of buying the whole bucket: