All on the Line · Mathematics
The path matters as much as the outcome. More investments fail from the path than from the thesis.
Path dependence
20 April 2026
5 minutes

In March 2021, Archegos Capital Management collapsed in a matter of days, triggering over $20 billion in losses across the banks that had financed it. The positions Archegos held weren’t obviously wrong. Several of the underlying stocks recovered meaningfully in the months that followed. But the path through which those positions had to survive — a sudden margin call, forced liquidations, a collapsing equity base — was incompatible with the system that was supposed to outlast it.
This is not a story about bad predictions. It is a story about the difference between a process and the path it takes to get there. That distinction is easy to overlook, and very expensive when you do.
Start with $100. If it grows at 10% per year, the path is uneventful. After one year, it is $110. Then $121. Then $133. Then $146. After five periods, it reaches $161. Each step builds on the previous one. The compounding feels intuitive because the sequence is smooth. Nothing forces a decision. Nothing interrupts the trajectory. The path and the outcome are aligned.
Now take a different sequence, starting from the same $100. The first move is −40%. The value drops to $60. Then it increases by 30% over the next four years: $78, then $101, then $131, then $171. After five periods, it ends 6% above the first path.
If the only thing that mattered were the final number, the second sequence looks better. If the only thing that mattered were average returns, the two sequences would look nearly identical — or even favor the second.
But that is not how the process is experienced.
For four out of five years, the second path is economically worse. It only catches up at the very end. Any constraint applied before that moment — capital requirements, reporting obligations, liquidity needs, investor patience — would treat it as the inferior path. The recovery happens, but only after the damage has already forced its consequences.
Consider the difference in a human register for a moment. A person who takes on a large mortgage and then loses their job faces this exact structure. The long-run math might still work. But the path through unemployment, missed payments, and foreclosure can destroy the position before the recovery ever arrives. The process was fine. The path was not survivable.
This is the first place where the representation begins to diverge from the experience. Both sequences can be summarized with a small set of statistics. But the system does not unfold as a summary. It unfolds one step at a time.
A return process is simple in structure: each period produces a return, and that return is applied to the current value. The sequence of returns defines the path. There is no mechanism that averages them out in real time. Each realization becomes the starting point for the next one.
What matters in practice is not that the process is random. It is that the sequence is where constraints are triggered. Capital is deployed at a point in time. Losses and gains occur in a particular order. Financing, liquidity, and decision-making are all tied to realized values, not expected ones.
Once you understand this, the earlier example stops being a curiosity. The two paths are not variations around a common center. They are different trajectories through the same space — one of which passes through a region where the system’s constraints become binding before the recovery arrives.
Now introduce leverage.
Take the same path — beginning with a 40% decline — but fund the position with $100 of equity and $100 of debt, for $200 in total assets. Assume the debt is fixed at $100 and carries a 5% annual cost.
Year 1: A 40% loss on $200 reduces assets by $80, from $200 to $120. After the $5 financing cost, total assets sit at $115. With debt still at $100, equity falls to $15.
The position does not enter Year 2 at the original 2x leverage. It enters at 7.7x. Losses compress the system immediately. Recovery takes time.
That was not a decision. It was the direct consequence of the path.
Year 2: A 30% return on $115 adds $35, bringing assets to $150. After the $5 financing cost, assets end the year at $145. Equity rises to $45.
Years 3 through 5: The recovery continues. Total assets reach $298 by the end. Equity rises to $198. The ending value is higher than in the unlevered case.
On paper, the process recovers. The sequence of returns has not changed.
But the system has.
After Year 1, 85% of the equity has been wiped out. The position is no longer operating under the assumptions that defined the original model. It is operating under a different capital structure, with a different level of fragility, and under tighter constraints than when it began.
In practice, most positions do not survive that transition. A drawdown of that magnitude triggers consequences before the recovery takes place. Margin requirements tighten. Covenants are breached. Liquidity disappears. The position gets closed — not because the long-run thesis was wrong, but because the path made it unfinanceable before it became unprofitable. This is precisely what happened to Archegos.
Most models are built to describe the process, not the path. They summarize the distribution, estimate parameters, and project outcomes. They compress the system into something that can be evaluated and compared.
But the compression removes the conditions under which the process actually operates.
The model assumes continuity. It assumes capital remains available. It assumes the process runs long enough for the expected outcome to emerge. The path determines whether any of those assumptions hold.
A leveraged strategy can show a positive expected return and acceptable risk metrics while still being exposed to sequences that terminate it early. A deal can produce an attractive projected return while still being sensitive to the timing of cash flows — delays in early periods create liquidity pressures that the projection doesn’t capture. A business can have stable long-term growth assumptions while still being vulnerable to early shocks that alter its trajectory permanently.
In each case, the issue is not that the model is wrong. The calculations can be precise. The assumptions can be reasonable. The divergence arises because the model describes the process, while the outcome is governed by the path — and the path determines whether the system itself remains intact.
Two earlier columns — An Average May Not Exist in Finance and The Lie of the Average — explored why summaries mislead: sometimes the average doesn’t exist at all, and sometimes it exists but describes no one’s actual experience. Both problems remain. But even when they are resolved, this one appears underneath them.
A process can be well-defined. The average can exist. The model can be correct. And the outcome can still be entirely different from what the model suggests — because the model describes where the process might go, while the path determines whether it gets there.
This changes the question you should be asking. Not only: is this process attractive in expectation? But: is the path required to realize that expectation compatible with the constraints of the system I’m actually operating?
Finance is typically optimized in expectations. Decisions are framed in terms of averages, projections, and long-run behavior. But the system is experienced through realizations, one period at a time, under constraints that do not wait for the average to emerge.
A smooth path produces a steady outcome. A volatile path can produce a higher final number — and still destroy the system before it arrives there.
The average describes the process.
The path determines whether the system survives long enough for the process to matter.
— Carlos E. Mora
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