Think of the last time a room rose to its feet around you. A performance ends, a few people stand, then a few more, and before your mind has decided anything, your own legs are lifting you out of the seat. You may not even have thought it the finest thing you ever saw. You stood because the room was standing. In that moment the crowd had stopped responding to the performance at all. It was responding to itself.
We do this constantly, and mostly it is harmless. We join the longer queue because it must be the better stall. We buy the book everyone is reading. We quicken our step a little when the people around us quicken theirs. There are two quite different ways to decide what to do in a crowd, and we slide between them without noticing. One is to weigh the thing in front of us on its own merits. The other is to watch what everyone else is doing, and do that. The first looks at the play. The second looks at the audience.
Most of the time, copying the crowd is a sensible shortcut. The crowd often knows something we do not, and following it spares us the work of judging everything for ourselves. But it has one strange property worth noticing now. When enough people decide by copying, there is eventually no one left doing the original judging. The crowd is copying a crowd that is copying a crowd, and the whole thing can drift a very long way from the thing it was meant to be about, with no one quite responsible for the drift.
Hold that distinction lightly for a moment, because it turns out to be the most important thing about a market. In the last two episodes we met two kinds of participant: the buyer who never looks at the price at all, and the buyer who looks at the price and leans against it, toward what they believe a thing is really worth. But there is a third kind we have only glimpsed, and they are the ones who look at the price and, like the person rising in the standing ovation, simply do what they see everyone else doing. To meet all three together, and to watch how they push and pull on one another, we need to go back, at last, to a particular bridge.
Back to the bridge
You will remember the bridge from our first episode. A sleek new footbridge opened across the Thames, and the moment a crowd streamed onto it, it began to sway. Not from wind, not from any fault, but from the people themselves. You could feel the deck tilt underfoot, the whole span alive with the crowd’s own movement. As the bridge made its first small wobble, each walker shifted their weight to keep balance, and because they all shifted the same way at the same instant, they pushed the bridge harder, so it swayed more, so they shifted again. A calm walk became a frightening lurch, and nobody had chosen it.
I asked you then to keep that bridge in mind, and now we can see what was truly happening on it. Picture the crowd not as one mass but as the individuals they were. Most of them did exactly what the motion encouraged: they felt the sway and moved with it, each correction feeding the next. But imagine, here and there, a few people who did the opposite. Feeling the deck tilt one way, they deliberately leaned the other, resisting the motion instead of joining it. Every one of those people quietly took energy out of the sway. Had there been enough of them, the bridge would have stilled. There were not, and it did not.
That is not a footnote about engineering. It is the exact shape of a market. A market, like that bridge, is a crowd whose members are all reacting to the same moving thing, the price, and feeding their reactions straight back into it. And just as on the bridge, what happens to the whole structure depends entirely on a hidden split inside the crowd: how many are leaning with the motion, and how many are leaning against it.
This is why the bridge is the truest picture in the whole series, and why we keep walking back onto it. It is not a metaphor for a market. It is the same machine: a crowd, a shared signal, and a loop running between the two. Change the mix of the crowd and you change what the machine does, from carrying people safely across to shaking itself apart, with nothing altered but the proportions of who leans which way.
The two questions that sort everyone
Most people, when they try to make sense of who is in a market, ask a single question: are they clever or foolish, informed or ignorant, paying attention or not? It is the natural question, and it is the wrong one. To understand what a participant does to a market, you have to ask two questions instead, and the second matters far more than the first.
The first question is the obvious one. Does this participant watch the price at all? Some do. They study it, react to it, care about it intensely. Others, as we have seen, do not. The blind buyer, the index fund, never looks.
The second question is the one almost everyone misses, and it is the key to this entire series. When the price moves, which way does the participant lean? Do they lean against the move, selling into a rise and buying into a fall, pulling the price back toward some idea of worth? Or do they lean with the move, buying because it is rising and selling because it is falling, pushing it further in the direction it is already travelling?
Those two questions, not one, are what sort a market into its true parts. And here is the surprising thing, the thing that quietly undoes the most comfortable belief people hold about markets. Watching the price closely tells you almost nothing about which way a person leans. You can watch the price like a hawk and steady the market. You can watch it just as closely and shake it apart. Attention is not the dividing line. Direction is.
The three crowds
Put the two questions together and a market falls into three crowds. We have already met two of them. The third is the one this episode exists to introduce.
The first crowd watches the price and leans against it. These are the value buyers from our last episode, the brakes, the depth of the water. They are the quiet contrarians, forever a little out of step with the room, selling the thing everyone is celebrating and buying the thing everyone has given up on. On the bridge, they are the rare figures who feel the sway and brace against it, and every trade they make takes a little energy out of the move. They are the stabilisers, and a market is steady in proportion to how many of them it holds.
The second crowd watches the price just as intently, and leans the other way. These are the trend followers, and their everyday cousins are the herd: the momentum buyer, the chaser of hot stocks, the crowd swept up in a mania, the person rising in the standing ovation. They are not foolish and they are not blind. Many are highly sophisticated, watching the price with enormous care. But they have made the opposite choice. They buy what is rising precisely because it is rising, and sell what is falling because it is falling. On the bridge, they are the great mass who feel the sway and move with it, every step feeding the next. And here is the uncomfortable revelation this episode has been building toward. This crowd watches the price every bit as closely as the stabilisers do, and they make the market less stable, not more. So the thing we instinctively trust, that as long as clever people are watching prices, prices will stay honest, turns out to be false. Half the watchers are pushing the wrong way.
In the last episode, for simplicity, we let the watchful stand for the stabilisers, as though everyone paying attention were on the side of calm. This is the fuller picture. The watchers were always divided, and only ever half of them were holding the price steady.
You have watched this crowd at work, even if you have never owned a share. It is the crowd that pours into a rising housing market because prices are rising, which makes prices rise further, which draws in more buyers still. It is the queue outside a bank that grows precisely because it is growing, each new arrival a reason for the next to join. It is the stock that doubles for no reason anyone can name except that it doubled last week. In each case the rise is its own cause, and the chasers are at once the effect and the engine.
The third crowd does not watch the price at all, and still it pushes. This is the blind buyer, the index fund, the sleepwalker with its eyes closed, and on the bridge it is the walker with headphones on, lost in their own music, who never feels the sway and yet whose every footfall still lands on the deck and still loads it. It does not mean to amplify anything. It simply moves with the flow of money in and out, and that flow, by buying most of whatever is already largest, happens to lean the same way as the trend follower: with the move, not against it.
Three crowds, then, on one bridge. One braces against the sway, and two, by opposite means, feed it. Keep all three in view, because everything that follows is a story about what happens to a bridge as the bracing thins and the swaying grows.
Which way you lean is everything
Step back and look at what we have. Three crowds. Two of them, the trend followers and the blind buyers, push the price further in whatever direction it is already going. They arrive at that destabilising effect by completely different routes, one by chasing the price on purpose and one by ignoring it entirely, but the effect on the structure is identical: both lean with the move. Only one crowd, the value buyers, leans against it. Only one supplies the bracing.
This is the idea the whole series turns on, so let me state it as plainly as I can. What holds a market together is not how many people are watching it. It is the balance between those leaning against the move and those leaning with it. A market thick with bracers can absorb a great deal of chasing and a great deal of blind flow and still hold steady, the way a bridge with enough steadying walkers can carry a crowd safely across. A market with too few bracers cannot. The structure does not care how clever anyone is. It cares only about the balance of the leaning.
And now the two threads of this series tie into a single knot. Recall what is happening to that balance, year upon year. On one side, the blind buyers grow, adding ever more mass that leans with the move. On the other, the bracers, the value buyers, are slowly being defunded and sent home, because they spend years looking foolish while a one-directional tide carries prices up regardless of worth. The destabilising mass swells while the stabilising mass thins. Both sides of the balance are tipping the same way, toward a market with less and less to lean against.
And the two crowds leaning the same way do not merely add together; they lend each other a hand. The blind flow lifts whatever is already largest, which is exactly the rising thing the chasers love to chase, so the headphone crowd quietly manufactures the very trends the trend followers then pile into and amplify. Each makes the other’s work easier. The bracing, meanwhile, has no such ally; it stands alone against the two of them.
And it stands more thinly than it looks, because not everyone who appears to be a bracer truly braces. A great many of the professionals paid to judge value live under the shadow of a benchmark, the index they are measured against. Drift too far from it and clients grow nervous; underperform for too long and careers end. So even among the watchful, many dare not lean very hard against the crowd, because to lean is to risk looking wrong and alone for years. On paper they sit in the stabilising camp. In practice they are pressing only lightly on the brake. Which makes the comforting thought, that a handful of clever investors will always be enough to keep prices honest, shakier than it sounds. The real steadying weight in a market is smaller than the headcount of professionals suggests, and it too is shrinking.
I want to be careful here not to cast anyone as a villain, because none of this needs one. The trend followers have always existed; markets have always contained people who chase. A healthy market simply held enough bracers to absorb them. What is new is not the chasing. What is new is the quiet draining away of the people who used to lean the other way.
The crowd you cannot simply blame
There is a powerful temptation, when a market lurches, to find the crowd responsible and punish it. Almost always, the crowd hauled into the dock is the second one: the chasers, the speculators, the ones who ride the move. When prices fall too fast, the first instinct of those in charge is to forbid the betting against falling prices, to name the riders as the cause and stop them.
It is worth seeing why this so rarely helps, because it goes to the heart of everything we have built. The riders are real, and they do amplify. But they are only half of the destabilising mass, and on a falling bridge they are not even the half that does the most damage. The deeper trouble is structural: a balance that has tipped, too much weight leaning with the move and too little leaning against it. You cannot cure a problem of balance by punishing one group inside it. Silence the riders and you have done nothing about the blind flow, and nothing about the slow disappearance of the bracers, who were the only crowd ever holding the thing steady. Worse, the bracers are the hardest to summon back and the easiest to lose, and no ban ever brought one home. To blame a single crowd is to treat a symptom and miss the disease.
We have run this experiment more than once. When markets have plunged, the authorities have stepped in and forbidden the betting against falling prices, confident they had found the culprit. The falls continued anyway, because the ban left the real machinery untouched: the forced, blind selling, and the simple absence of anyone willing to buy. They had quietened one voice in the room and mistaken it for silence.
Which leaves the real question, the one this whole series has been walking toward, and the one we take up next. It is not the mere existence of the chasers that threatens the bridge, nor the obliviousness of the headphone crowd. Markets have carried both for as long as they have existed. It is the balance, and the slow tipping of it. And a balance, unlike a slope, does not give way gently. It holds, and holds, and then it goes, all at once, at a point you cannot see coming until you are already past it. What that point is, and why a market can look perfectly calm right up until the instant it changes its nature entirely, is where we go next.
For now, carry one picture out of the room with you.
"The only people steadying the bridge are the ones leaning against it, and they are the ones being asked to leave."
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.
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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.
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