Leverage: The Fuse That Turns a Good Portfolio into a Bomb

「Asset Allocation」 series · Final post on risk layers, and the series wrap-up. Framework in the opening article. Every chapter before this has been about "how to live long." This last one is about the one thing most likely to make you "not live long"—leverage.

011. The Temptation of Leverage: It Looks Like a Free Accelerator

Leverage—borrowing money to invest, using margin to amplify your position—is one of the greatest temptations in investing.

Its allure comes from a seemingly bulletproof logic: If my investment thesis is correct, why not borrow to amplify it and make even more?

Suppose you expect an asset to rise. If you buy with your own USD 1 million, a 20% gain nets you USD 200,000. But if you borrow another USD 1 million and buy with USD 2 million, a 20% gain nets you USD 400,000—the same correct call, but leverage doubles your profit.

This logic is seductive. It makes leverage look like a "free accelerator"—as long as you're right, leverage makes you more money, faster. Countless people have been lured step by step into the abyss by this logic.

Because hidden within is a deadly, conveniently ignored premise: "As long as you're right."

And the problem is—even the smartest people get it wrong sometimes. And leverage will kill you on that one wrong call.

022. The Truth About Leverage: It Amplifies Not Gains, but Consequences

The truth of leverage can be summed up in one sentence: It doesn't change whether you're right or wrong; it only magnifies the consequence. You fly if right, die if wrong.

And its most lethal feature isn't simply "magnifying losses"; it's that it triggers an irreversible destruction mechanism—forced liquidation.

Imagine you use 2x leverage (borrow USD 1 million, invest USD 2 million). If your bet is wrong and the asset falls—

A 25% decline: your USD 2 million becomes USD 1.5 million, but you still owe USD 1 million. Your equity is only USD 500,000 (half of your original USD 1 million).

At a certain point, your broker force-liquidates—it doesn't care about your conviction, whether this is a temporary plunge, or whether the market will bounce tomorrow. It will sell your assets at the worst possible moment, grab back what it lent you first.

This is the destruction mechanism of leverage: It turns a "temporary paper loss" into a "permanent, forced-realized loss."

Someone without leverage can choose to "hold, not sell, wait for the rebound" during a crash (remember the cash article—the right not to be forced to sell). But someone using leverage doesn't have that option—once the asset hits the liquidation line, they are forced out. It no longer matters whether their thesis was right, because they've been kicked off the table and won't live to see the rebound.

The cruelest part: leverage forces you to sell at the very moment you most shouldn't—the bottom. It strips you of the ability to "ride out a crash"—which is the single most important ability in long-term investing.

033. Why "Being Right Most of the Time" Won't Save You: You Only Need to Be Wrong Once

Proponents will say: "I have good judgment, I'm right most of the time, so leverage works for me."

This is the most dangerous misunderstanding of leverage. Because with leverage, being right most of the time can't save you. You only need to be wrong once (or even not wrong, just hit by a deep enough drawdown) to be wiped out.

This echoes Taleb's repeated point about ergodicity (remember Fooled by Randomness)—for an individual, one catastrophic failure means you're out, with no "do-over."

Imagine a leveraged investor who is right 95% of the time and makes a lot of money. But then comes that one time—a big bet that goes wrong, or a market panic that triggers his liquidation line even though he was fundamentally right—and that single event can wipe out all the gains from the 95% victories, principal included, and even leave him in debt.

This is the fundamental difference between leverage and no leverage: without leverage, you can be wrong and recover (losses are temporary when you don't sell); with leverage, one wrong call can permanently knock you out (forced liquidation, no recovery).

Over a multi-decade investing career that inevitably includes multiple crashes—the question is not "will you ever be wrong?", but "when will you be wrong?". Over a long enough timeframe, everyone will encounter that one time. For someone without leverage, it's "a drawdown." For someone with leverage, it could be "game over."

The victory of long-term investing doesn't belong to those who win the most, but to those who can stay at the table (the core of the framework). And leverage is the fastest way to be kicked off the table.

044. Where I Differ from the Mainstream: For the Vast Majority, the Answer Is Zero

The mainstream attitude toward leverage is usually "use it in moderation, control the risk"—as if it's a neutral tool that can be good or bad.

My stance is more extreme, and more direct: For the vast majority of individual investors, the correct amount of leverage is: zero.

Why so absolute? Three reasons—

First, the "penalty" of leverage is asymmetric and irreversible. As discussed—when leverage works, the gain is linear (double the return); but when a loss triggers liquidation, the outcome is "permanent ruin." This asymmetry—limited upside amplification, possible downside to zero—is anti-convex (remember Taleb, the Bitcoin piece—good bets are convex; leverage is the opposite: downside is unbounded, upside is bounded). A rational allocator should seek convexity and avoid anti-convexity. Leverage is the most typical anti-convex structure.

Second, you cannot predict crashes, so you cannot use leverage "safely." Proponents think they will "deleverage in time when danger comes." But crashes are unpredictable (remember complex systems, black swans)—they come fast and suddenly (March 2020: 34% drop in a month). By the time they hit, you won't have time to "deleverage in time"; you'll just get force-liquidated. "I'll get out in time" is a dangerous illusion—it assumes you can predict something you fundamentally cannot.

Third, you don't need leverage to get good enough long-term returns. Stocks have returned 6–7% real annually over long periods. Compounded over decades, that is enough for a disciplined, consistent investor to meet financial goals (remember Siegel, remember the 30-year portfolio piece). You don't need leverage to "accelerate"—you just need to avoid being knocked out by any single crash and let time and compounding do their work. Leverage is precisely the thing that will get you knocked out and prevent you from ever realizing those compound returns. It's not an accelerator; it's a detonator.

To be fair, there are a very few professional players (like Ed Thorp) who, with rigorous mathematical models and risk controls, can safely use leverage in specific strategies (remember Beat the Dealer, Fortune's Formula). But they have tools, discipline, and hedges that ordinary people lack. For the vast majority who don't have these—leverage is not a tool that, if used well, can accelerate; it is a fuse that will, sooner or later, blow up in your face. The answer is zero.

055. The Invisible Forms of Leverage: You Might Be Using It Without Knowing

One final note—leverage isn't just "explicitly borrowing to buy stocks." There are many invisible forms you might be using without realizing it—

Leveraged ETFs (2x, 3x long): They embed leverage, and because of daily rebalancing, long-term holding suffers severe "volatility decay." They are designed for day trading, not for long-term holding.

Options: Many option strategies contain high leverage. Buying out-of-the-money call options to bet on a big move is essentially a leveraged gamble (though downside is limited to the premium, which is better than margin—but the high probability of going to zero makes it equally dangerous for ordinary investors).

Margin accounts: The most direct form of leverage, with clear liquidation lines.

Using consumer loans / mortgage money to invest: One of the most dangerous invisible forms—you think you're "investing your own money," but if that money is borrowed (even at low mortgage rates), you are using leverage and face the risk that the investment loses money while the debt still has to be repaid.

Even "fully invested + no cash" is a form of hidden fragility—not borrowing, but it strips you of the ability to "not be forced to sell during a crash and to have cash to buy on the cheap" (remember the cash article), leaving you potentially forced to sell at the bottom to meet unexpected expenses.

Identifying and steering clear of these invisible forms of leverage is as important as avoiding explicit margin. The essence of leverage is "investing with borrowed money or money you can't afford to lose, thereby losing the ability to ride out a crash"—whatever form it takes.

066. In Closing: The Series Wrap-Up

This is the final piece on risk layers, and the closing chapter of the entire Asset Allocation series. Ending with leverage is intentional—because leverage is the ultimate test of the entire allocation framework.

We spent a whole series discussing how to construct a portfolio that can "survive all possible futures and live long"—strategic framework (don't bet on a single future), asset pairing (true diversification with low correlations), execution discipline (rebalancing, DCA, low costs), risk defense (allocate based on your ability to bear risk, avoid pseudo-diversification, guard against sequence risk).

And leverage can destroy all that effort in an instant.

A perfectly diversified, disciplined, low-cost, risk-matched portfolio—if levered—can be reduced to ashes in one forced liquidation during a crash. Leverage is the fuse—it can turn your carefully constructed, steady portfolio into a bomb, and detonate it at some unpredictable moment.

So, if from this entire series only one sentence could remain, I hope it's this—Investing victory doesn't belong to those who make the fastest money, but to those who live the longest. And the first rule of living long: never place a bet where one mistake can take you out. Leverage is exactly that kind of bet.

This perfectly echoes the core message from the opening piece: Don't predict the future; prepare for all futures.

You can't predict when a crash will come. But you can ensure that when it does, you are still alive.

No leverage, hold cash, true diversification, match your risk capacity, guard against sequence risk—the ultimate purpose of all of this is one: to keep you at the table no matter what, and let time slowly hand victory to the one who 'lives to the end.'

All the wisdom of asset allocation, from the framework to this final piece—nine layers, over a dozen articles—condenses into one brutally simple sentence:

First, don't die. Then let time win for you.

And leverage is the thing that makes you "die first."

So for it, the answer is zero.

—

This wraps up the Asset Allocation series. From the framework ("prepare for all futures") to strategic frameworks (60/40, All-Weather, framework selection), asset pairing (cash, bonds, gold, Bitcoin, international, broad index), execution and maintenance (rebalancing, DCA, costs, 30-year portfolio), and risk defense (drawdowns, pseudo-diversification, sequence risk, leverage)—they form a complete map.

At the center of the map, that sentence remains: Don't predict the future; prepare for all futures.

May it serve you well.