Finn Brooks: Okay, hey — so I did something embarrassing to prep for today. I actually pulled out a calculator and just... ran the numbers myself. Like, didn't trust the research.
Clara Bennett: And?
Finn Brooks: And it's real. A fifty percent loss — you need a hundred percent gain to get back to zero. I kept re-entering it thinking I'd made an error.
Clara Bennett: That instinct to recheck it is actually the whole episode. The math isn't hidden — financial leverage is a perfectly legible mechanism. You borrow capital, you control a larger position than your own equity permits, you collect the upside on the full position. The definition is right there. And yet Philip Newall's research shows investors treat the downside as if it's symmetrical with the upside, and it — structurally — is not.
Finn Brooks: So we keep being wrong about this in the same direction? Like, not randomly wrong — consistently wrong?
Clara Bennett: Consistently, and in the direction that benefits the trade going in. That's what makes it unsettling.
Finn Brooks: Okay but — I want to make sure I actually understand the engine before we get to where it breaks. Like, strip it all the way down. You borrow money at five percent, you invest it at ten percent, you just... keep that five percent spread on every dollar you borrowed. Not just on your own money. That's it, right? That's the whole trick.
Clara Bennett: That's it. Now put numbers on it — say you have a hundred dollars of your own, you borrow another hundred at five percent, invest the full two hundred at ten percent. You earn twenty dollars, pay five in interest, net fifteen on your original hundred. That's a fifteen percent return on your equity versus ten percent if you'd never borrowed.
Finn Brooks: Wait so — fifteen versus ten — just from borrowing?
Clara Bennett: Just from borrowing. The formula is ROE equals return on assets plus that spread — ROA minus cost of debt — times your debt-to-equity ratio. The multiple does the amplifying. Two-times leverage means two-times the gain. But — and this is the part that doesn't feel symmetrical until you stare at it — it's also two-times the loss.
Finn Brooks: So the same mechanism. Identical. It doesn't — like, it doesn't know which direction the market is going.
Clara Bennett: Exactly. Leverage doesn't create upside — it amplifies whatever direction the asset moves. The formula is perfectly neutral. And that's actually the clean, satisfying version of this story, which is why most explanations stop there.
Finn Brooks: But that's not — wait, that's not the whole story, is it? Because if the math is this clean and this knowable, why do we keep getting crashes? Like, 2008, the 2015 Chinese market dropping forty percent in one month — smart people had the formula.
Clara Bennett: Because the formula stops mattering the moment a lender calls. That's the mechanism people skip. A margin call isn't a consequence of leverage going wrong — it's leverage's structural response to falling prices. Collateral erodes below a required threshold, the lender demands cash or forces a sale, and now you're not an investor making a decision. You're a seller with no choice.
Finn Brooks: Okay, that — that hits different. Because Tuesday morning, 2007, right? Imagine a hedge fund manager, completely competent, running three-times leverage on mortgage-backed securities. Yields are solid, he's beating his benchmark by two percent. Everything is fine. And then — wait, not even because his thesis was wrong —
Clara Bennett: He's selling good assets at fire-sale prices because he has to.
Finn Brooks: Not to fair value. Below it. That is — that's the part that wrecked me.
Clara Bennett: And Thurner, Farmer, and Geanakoplos — the Yale Cowles Foundation research — they modelled exactly this. Not reckless funds, not irrational actors. Rational value-investing funds using leverage together, and the model still produces fat tails and clustered volatility. The instability isn't behavioural. It's structural. The mechanism generates it.
Finn Brooks: Which — okay, the Chinese market. June 2015. Second-largest stock market in the world, all-time high, and then forty percent gone in one month. One month. People were comparing it directly to 1929.
Clara Bennett: The Federal Reserve Bank of New York documented the same pattern in 2008 — leveraged investors amplifying the collapse, not just caught in it. And what that research actually surfaces — I mean, this is the part worth sitting with — maximum fragility is already locked in at the peak. Right before the turn. The leverage cycle expands during good times, competition pushes everyone higher, and the system is most fragile exactly when it feels safest.
Finn Brooks: Wait so the danger signal is... the good times?
Finn Brooks: Yeah. The danger signal is the good times. And I keep — I mean, that's the game theory thing that I can't shake loose. Like, if I'm a fund manager and everyone around me is leveraging up and posting great returns, the individually rational move is to do the same thing. I'm not being reckless. I'm keeping up. But we're all collectively just... loading the gun. Maximizing fragility at the exact moment the leverage cycle peaks. And I don't know — does better regulation actually stop that? Or does the pressure just move somewhere the rules don't cover yet?
Clara Bennett: That's the question the IMF has been circling for years without a clean answer. Better margin rules, circuit breakers — in practice, they may just restructure where the risk accumulates, not reduce it. And every bull market makes leverage cheaper and more available again. The cycle resets.
Finn Brooks: You remember what I said at the top — I kept re-entering the numbers thinking I'd made an error?
Clara Bennett: Mm.
Finn Brooks: I hadn't made an error. That's sort of the whole thing, isn't it.
Clara Bennett: It is. Good talk.
