Actionable insights — Kaplan's Pain Index

1. Score a drawdown as depth × duration, then index it to a known crash

1. Record two numbers for the episode: the peak-to-trough fall in per cent, and the years taken to regain the peak.
2. Multiply them to get the pain surface: drawdown (%) × recovery time (years).
3. Divide by a fixed reference — the 1929 crash, 79% over 4.5 years = 355.5 — so every episode is expressed as a percentage of a crash everyone already understands.
4. Use the index to rank episodes, and to sanity-check how the current one compares while it is still running (estimate the recovery time, and re-estimate as it lengthens).

• The recovery clock still running. An index computed mid-crash understates the score by definition, and the understatement grows the longer the crawl lasts.

2. Weight recovery time above drawdown when judging what you can withstand

1. Rank historical crashes by the pain index rather than by headline drawdown, and note where the two rankings disagree.
2. Recognise that the formula's equal weighting still understates duration: "investors don't experience them equally. Investors suffer most from a long recovery time."
3. Stress-test your own plan against a long shallow episode, not just a violent one — the shallow-and-long case is what breaks discipline.
4. Set your position sizing and cash needs against that scenario.

• Risk measures built only on maximum drawdown. They price the fear, not the attrition.

3. Plan for the lost decade as a normal, recurring event

1. Define it precisely: ten years or more in which the market rises but not enough to beat inflation — a real-return drought, not necessarily a falling index.
2. Note the base rate: three since 1900 — 1914–1945, 1973–1985, 2000–2012 — which is a meaningful share of any investing lifetime.
3. Build the plan so that a decade of no real return is survivable: contributions that continue, spending that does not depend on gains, and an approach you can hold without confirmation.
4. Measure real returns, not nominal ones, so you can tell whether you are in one.

• Nominal charts hiding it. A lost decade often looks like a modestly positive market until inflation is deducted.

4. Choose the buying mechanism that matches the market you might get

1. Fix a date and an amount and buy on schedule, removing the decision from the moment.
2. Understand precisely when the mechanism wins: in flat-to-falling markets, later purchases are made at lower prices, so the average cost falls below a single up-front entry.
3. Test it on the worst historical stretch you can find, comparing the same total capital deployed both ways.
4. Be explicit about the trade-off — in a rising market the lump sum wins — and choose on the basis of which error you can live with.

• The missing counterexample. The article does not show the rising-market case, where the same discipline costs money — DCA is bought volatility protection, not free return.

5. Treat your own reaction as the risk being managed

1. Name the failure sequence in advance — self-doubt, emotion, then discipline fading — so it is recognisable when it starts.
2. Automate the decisions that the sequence would otherwise corrupt: the purchase date, the amount, the instrument.
3. Judge a strategy by whether you can execute it through the worst case on your own index, not by its back-tested return.
4. Accept the conclusion literally: "The real risk isn't the market, it is how you react to it."

• Automation that is only nominally automatic. A monthly transfer you can cancel in an app is exactly as strong as your worst month.