Size: a regime, not a rule

A friend forwarded me a small-cap fund chart on Sunday morning. Five years, straight up and to the right. His question was simple: if small beats large, why isn't my whole SIP sitting in small caps?

It is a fair question. The answer is the part the brochure quietly skips.

Small beats large is real, in the textbook. Banz documented the size premium in 1981 at roughly 5.2 pct a year. It built a thousand fund factsheets. Then the paper got read, the money came in, and the edge did what crowded edges do. Out of sample since, the premium reads closer to 1.5 pct. Around 71 pct of it has decayed.

You can see the same thing up close without any academic paper. Take the same equal-weight engine and the same fortnightly rebalance, change only the cap segment, and the cap curve flattens fast. Allcap 48.02 pct CAGR. Midcap 41.21. Smallcap 41.03. Microcap 40.56. The return barely moves as you go smaller. The drawdown keeps deepening, from minus 22.7 pct down to minus 26.4 pct. Microcap gives back almost half a point of return for four points more pain. (Backtest, illustrative, not a guarantee.)

Here is the part that matters. The premium that survived is not a reward for being clever. It is compensation for illiquidity and distress risk. You get paid to hold what other people cannot sell in a hurry. So it pays in one kind of weather and reverses in the other. Early cycle, liquidity loosening, small caps cheap and uncrowded, it works. Late cycle, risk-off, everyone already in, it hands the book back.

So size is a tilt, not the whole portfolio. Read the regime, not the twenty-year average. Pick a weight you can SIP through nine straight red months, then stop touching it.

Small beats large in the right weather. The rest of the time you are renting volatility and calling it a factor.

The cap curve, updated

The figures in the opening were the ones published in May. Here is the same cap curve from the current lineup file. The shape held: going smaller did not add return, and it did not reduce the worst fall. Allcap shows a 44.70 percent CAGR with a worst fall of 22.72 percent, Midcap 38.75 percent and 24.87 percent, Smallcap 37.40 percent and 22.34 percent, Microcap 37.33 percent and 26.43 percent (Model, back tested, as of 27 Apr 2026).

All four rank on momentum inside their own NSE universe and rotate every two weeks. So the comparison isolates one thing, the size of the companies, and on this window size alone paid nothing extra.

What NSE's size indices did in the last two years

The real indices tell the regime story directly. From 9 Oct 2024 to 9 Oct 2026, the Nifty Microcap 250 ended 1.34 percent higher on price while the Nifty 50 ended 9.85 percent lower. Smaller won on the destination. Look at the bracketed falls along the way, though: the deeper the universe, the deeper the hole.

The swings tell the same story. Over those two years the Nifty Microcap 250 moved with 21.3 percent annual volatility, the Smallcap 250 with 18.9 percent and the Nifty 50 with 13.2 percent. And the long view is harsher still: the Smallcap 250 lost more than half its value between January 2018 and March 2020, and buyers near the 2018 top waited years to get back.

The weather report: what you pay today

The opening says the premium pays when small caps are cheap and uncrowded. On 9 Oct 2026 NSE showed the Smallcap 250 at 34.0 times earnings and the Midcap 150 at 28.1, against 19.3 for the Nifty 50. That is not the cheap and uncrowded weather. A premium earned from a high starting price has less room to run.

The illiquidity you are paid for, in rupees

Compensation for illiquidity sounds abstract until you place an order. Say a small company's shares trade Rs 40 lakh a day on average. A Rs 2 lakh order is 5 percent of a normal day: you nudge the price, but you get in. A Rs 20 lakh order is half the day's trade, and you push the price against yourself going in and again coming out. That cost never shows on a chart of the index.

The free Learn module on the size factor covers the NSE size ladder, liquidity and how to size a small cap sleeve, with a quiz. The posts on size against junk and factor crowding take the decay argument from the opening further.