I am a trend follower by trade, which is to say I make my living as one of the very crowds this series treats with suspicion: the people who lean with a market’s movement rather than against it. That is worth admitting at the outset, because it shapes both what I can see and what I am inclined to miss. I did not arrive at these ideas as a detached observer. I came to them as a practitioner who began to feel, over several years, that the ground beneath all of our models was shifting, and that the language we usually use to describe markets was no longer quite capturing what was happening to them.
What I kept reaching for, in the end, was the language of complex adaptive systems. Markets are not machines with knowable parts. They are ecologies of interacting agents, and ecologies behave in ways that confound our intuitions. They hold steady and then tip. They grow calm precisely as they grow fragile. The forces that stabilise them in small doses destabilise them in large ones. None of this is visible if you look only at prices and fundamentals, but all of it comes into focus the moment you look at the market as a living system of feedback. That shift in vantage, from the parts to the pattern, is what this series tries to hand to an ordinary reader.
I wrote it in plain English, and deliberately so. The argument it carries is not, for the most part, mine, and in its rigorous form it is technical and demanding. But its conclusions touch everyone who owns a pension, and they bear on decisions that will be taken, over the coming decade, by people who are not specialists. An argument this consequential should not stay locked inside academic papers and practitioner podcasts. So I have tried to carry it across, picture by picture, into language anyone can follow, without, I hope, blunting its edge.
Whose work this stands on
I want to be clear, because it matters, that I have only recently joined a conversation that others have been leading for years, and that the substance of this series is built almost entirely on their work.
The heaviest debt is to Mike Green, of Simplify Asset Management, who has spent the better part of a decade arguing, against considerable resistance, that passive investing is not the neutral, benign force it is almost universally assumed to be. The central mechanism of this whole series, the price-blind buyer that purchases on inflow and sells on outflow without ever judging value, was his insight long before it was mine, as is the argument that this mechanical bid makes markets steadily more inelastic, and the warning that the demographic tide which filled these markets will one day reverse. I have spoken with Mike only once, in a single online conversation about the seriousness of the problem, in which I mentioned that I meant to write on it and he was kind enough to encourage me. The debt this series owes him is almost entirely to his published work, not to any claim of collaboration. Where these pages are clear, they lean on his thinking. What remains muddled is my own.
The second great debt is to Hari Krishnan, of SCT Capital Management, whose work on the structural fragilities that accumulate inside markets dominated by a few large agents, set out in his earlier writing on market tremors, gave many of us the vocabulary for thinking about these risks at all. More recently, Hari, together with Mike Green and Stephan Sturm of Worcester Polytechnic Institute, has placed the argument on a formal footing. Their paper, A Model for Passive That Breaks the Market, circulated on SSRN in March 2026, builds a model of the equity market that treats the passive share as a key variable, and reaches a sobering conclusion: that beyond a critical level of passive ownership, volatility begins to feed on itself, and the market is driven into ever more exaggerated cycles of boom and bust. They are careful, to their credit, to present their thresholds as outer boundaries rather than forecasts, and to note that more realistic assumptions, declining flexibility among active managers, correlated flows, demographic withdrawals, only bring those boundaries closer. The whole of my fourth episode, on the tipping point, is an attempt to render their formal result in plain words.
I am indebted, too, to the conversations in which these ideas have been aired, and to the people who have aired them. Niels Kaastrup-Larsen, whose podcast Top Traders Unplugged I am fortunate to join as a co-host, has built the room in which a great deal of this thinking now happens, and his recent conversation with Hari Krishnan and Cem Karsan, drawing on that same paper, sharpened my sense of how the pieces fit together, especially the part played by flows, positioning and policy in a system that may now drive the economy rather than merely reflect it. Cem’s work on the way flows and dealer positioning shape a market sits behind more of these episodes than the text lets on. And I owe a particular image to Keith McCullough, whose insistence that a market in transition does give signs, the gathering bubbles before the boil, to the observant eye, shaped the whole of my fifth episode.
I should add that this warning is neither new nor solitary. There is a community of investors who specialise in protecting portfolios against disaster, the discipline the trade calls long volatility, and they have been sounding this particular alarm for many years. The two I have already named, Mike Green and Hari Krishnan, belong to it; so do figures such as David Dredge of Convex Strategies, Wayne Himelsein of Logica Capital, and Nassim Taleb, whose writing on fragility and on rare, ruinous events has shaped how a generation thinks about risk. It would be easy to wave all of this away as salespeople talking their book, since protection is what they sell. But that reverses the true order of things: they came to sell protection because they had understood the fragility first, and they were describing these mechanics long before the passive share reached the levels that now concern them. The alarm is the fruit of deep and patient study of how markets actually work, not of any marketing calendar. I find them convincing not because they are worried, but because of how carefully, and for how long, they have explained exactly why.
If there is anything in this series that is genuinely my own, it is only the framing: the decision to treat the entire phenomenon as a problem in complex adaptive systems, and to carry it into plain English. The alarm itself belongs to the people named above. I have tried to translate it, and to add the systems lens that, as a practitioner watching one side of the machine from the inside, I happened to be standing in a useful place to see.
The argument, episode by episode
The series moves in a single arc, from what passive investing actually is, through how a market becomes fragile, to how it breaks and what survives the breaking.
Episode 1, The Buyer Who Never Looks at the Price. Introduces the price-blind buyer, the mechanical flow that now moves much of the market, buying and selling by size and indifferent to value, and makes the case that a buyer which is merely blind is not the same as a buyer which is neutral.
Episode 2, Why a Market Needs an Argument. Explains what a price actually is: not a fact stamped on a company but the settled outcome of a disagreement, and shows that the people who keep that argument honest, the value buyers who lean against every move, are the same people who give a market its depth.
Episode 3, The Three Crowds on the Bridge. Sorts the market into those who lean against the move and those who lean with it, and argues that stability depends not on how closely people watch the price but on the direction in which they lean.
Episode 4, The Day the Pond Becomes Ice. The pivot. It teaches the idea of a phase transition, that a system can hold its shape and then change state all at once, at a hidden line, and argues that a market can cross that line not through frenzy but through the quiet subtraction of the people who used to steady it. This is the episode that renders the Green, Krishnan and Sturm result in plain language.
Episode 5, The Stillness Before. Which gives the series its name. It teaches the reader to read the faint warning signs a fragile system gives, the recoveries that lengthen, the persistence that should not be there, and above all the treacherous calm that is not peace but the receipt for its loss.
Episode 6, Everyone Reaches for the Same Small Door. Follows the break itself: the shock absorbers that heal small falls but reverse in large ones, the demographic tide that turns a generation from buyers into sellers, and the three sellers who arrive at once through a door the buyers left long ago.
Episode 7, An Umbrella Is No Use in a Tsunami. Weighs the defences and finds them real but limited. Protection must be matched to the depth of the storm, the deepest protection depends on a promise someone must still be solvent to keep, and the authorities, being players inside the system rather than referees above it, can suppress a fall without curing its cause.
Episode 8, The Market That Keeps Talking After It Dies. Closes the series by reframing what the end actually looks like: not a silent, shuttered exchange, but a market that goes on trading long after price discovery has died inside it, a husk still quoting a number, a star still shining after it has burned out.
What I hope it does
I have tried, throughout, to keep faith with three commitments.
The first is that this is not a prophecy. I have named no date, because there is none to name, and I have said plainly, in the fifth episode and again at the close, exactly what evidence would show the whole argument to be wrong. A claim worth making is one that can be checked, and the reader now knows what to check.
The second is that no one in this story is a villain. The saver, the fund, the retiree, the regulator: each behaves entirely reasonably, and the danger is the property of none of them and of all of them at once. This is the deepest lesson of a complex system, and the reason the risk has been so easy to miss. It is written into the structure, not into the characters.
The third is that there is something to be done. The fragility I describe has, beneath all its contributing strands, one cause that runs through them, too few people rewarded for the patient work of judging value, and therefore one repair that matters more than any other: to value that work again, so that the steadying crowd is rebuilt rather than drained away. That is a choice, not a fate.
There is more to say than eight plain-English episodes can hold, and a longer and more formal treatment of these ideas is the work that follows this one. But if this series does only a single thing, I would like it to be this: to leave the reader able to tell the difference between the stillness of safety and the stillness that comes before something tips. We have spent a long time learning to fear the storm. The thing worth watching was always the unnatural calm.
Richard Brennan writes on systematic trading, complex adaptive markets, and the philosophical foundations of trend following at atstradingsolutions.com. His books include The Fractals of Finance and Complex Adaptive Markets. The forthcoming Carved by Impossibility completes the trilogy.
Want the theoretical foundation for why trend following works?
The Fractals of Finance: Determinism, Adaptation and the Geometry of Markets
The book explores the full architecture of feedback, fat tails, and fractal structure in financial markets, and what it means for how we trade, invest, and understand risk.
Available now on Amazon in paperback, hardcover, and Kindle.
Want a practical field manual for trading trends and capturing outliers?
The Aussie Turtles Trend Following Guide: A Field Manual for Hunting Outliers adapts the timeless principles of the original Turtle traders into a systematic, rules-based approach for modern markets. Co-authored with Adam Havryliv.
Available now on Amazon in paperback, hardcover, and Kindle.