How Low-Volatility Investing Works

What it selects for

Ramesh is a few years from retiring and has been offered something described as lower risk than the market but still equity. That is an appealing thing to be offered at his stage, which is why it is offered at his stage.

A low-volatility strategy ranks shares by how much their prices have moved about over some past period, and holds more of the ones that moved least. Some versions also take account of how the shares move relative to one another, aiming for a portfolio that is steadier than its parts.

Note what is being measured: past price movement. Not the quality of the businesses, not their debts, not how likely they are to lose money permanently. The rule sorts on one statistic computed from a price history.

Why it might work

It is one of the factor strategies, so the two competing explanations in how factor investing works apply here too, and they take a specific form.

The behavioural account. Investors who want a large gain and cannot or will not borrow to get it bid up the prices of shares that move a lot, because those offer the possibility of one. That leaves steadier shares relatively cheaper and therefore better value. If this is the explanation, the effect depends on that preference persisting, and it can be competed away as more money pursues it.

The structural account. Many professional investors are judged against a benchmark, which makes holding something very different from the benchmark risky for them personally even when it is sensible for the client. That discourages holding steady shares in size, and the discouragement persists because the incentive persists.

Both are plausible, neither is settled, and the difference matters for the same reason it does with any factor: one story implies persistence and the other implies decay.

The hazard specific to this one

Here is what makes this strategy different from the others, and it is a naming problem with real consequences.

Low volatility is not low risk. The strategy selects on past price movement, and price movement is not the same as the chance of an outcome you cannot accept — the distinction in risk against volatility.

Three specific gaps follow. A share can move very little and still fall permanently, because stillness in a price series is not a statement about the business. A share can be steady precisely because it is not traded much, in which case the low measured movement is an absence of prices rather than an absence of movement. And past stillness need not continue — the ranking is computed from a period that has ended, and companies change.

The consequence for Ramesh is that a fund described as lower risk may be sold to someone who needs their money soon, on the strength of a word that was measuring something else. A low-volatility equity fund is still an equity fund, and it will fall when the market falls. Less, perhaps. Not little.

What you give up

The proposition is most of the return with less of the turbulence, and the second half comes at a price.

Steadier shares tend to lag when markets rise strongly, which is the necessary counterpart of losing less when they fall. Over a full cycle a strategy that captures two-thirds of the fall and two-thirds of the rise has done nothing that could not have been arranged by holding some of the money in a deposit — at lower cost, and without depending on a rule continuing to work. That comparison is the one to make, and it is the argument set out in does past downside protection predict future protection.

There are also concentration effects. A rule selecting for stillness tends to select from particular industries, and portfolios built this way can end up heavily weighted towards a few of them — a concentration arriving through a rule rather than through a decision. Worth checking against the actual holdings: measuring concentration and overlap.

And it costs more than a plain index fund, which is certain, while the benefit is not.

The honest gap

This page quotes no figures for how a low-volatility strategy has performed in India, how much of the market's fall it captured, or whether the effect has persisted here.

All three need return histories for factor-sorted portfolios of Indian shares across several cycles, which needs constituent-level data. This repository holds one index series and inflation. Results measured in other markets rest on different companies, different investors and different costs, and are not transferable.

There is a further difficulty specific to this strategy, and it is the one an evidence-minded reader should hold on to: testing whether downside protection persists requires ranking on one period and checking a later one, across several separate downturns. India's record contains only a handful of major declines, so even with perfect data the sample would be small — which is a limit on what could ever be shown here, not just on what we currently hold.

What to take away

Low-volatility investing sorts shares by how much they have moved and holds the calmest. The mechanism is real, the explanations for why it might pay are unsettled, and the cost is lagging in strong markets.

The thing to guard against is the name. It selects on price movement, which is not risk, and it is offered most often to people who are approaching the moment when the difference between the two matters most. If what Ramesh needs is money that will certainly be there in a few years, the answer is holding less in shares — not holding shares that have recently been quiet.