How long were you under water?
Depth is only half of a drawdown. The other half is time — how long the portfolio spent below its old high before it saw that level again. Two declines of identical depth, one lasting eight months and one lasting eight years, are not the same event in any way that matters to the person holding it.
Two clocks, not one
Every drawdown has two durations worth measuring separately:
- Time to trough — from the peak to the lowest point. This is the falling phase.
- Time to recovery — from the trough back to the old high. This is usually the longer one.
Time under water = time to trough + time to recovery — the full stretch from the last high to the next high.
Two illustrative episodes
These are rounded and approximate; the exercise below has you verify them yourself.
Broad US large-cap equity, 2007–2013. The index peaked in October 2007, bottomed in March 2009 roughly 57% lower on price, and regained the old peak in the spring of 2013. Time to trough: about 17 months. Time to recovery: about four years. Total time under water: roughly five and a half years.
US technology-heavy index, 2000–2015. Peaked March 2000, fell about 78% by October 2002, and did not print a new high until 2015 — around fifteen years under water. Whatever the long-run average annual return of that index looks like on a chart, this is what a large part of it felt like from the inside.
The underwater curve
Plot the drawdown series through time and you get the single most honest performance chart there is. It sits flat at zero whenever the portfolio is at a new high, and dips into negative territory the rest of the time. The area and the width of those dips are the investor's experience — the equity curve shows the destination, the underwater curve shows the journey.
Here it is, on an authored path, drawn as a percentage of the running high rather than as a negative number — same series, same dips, one baseline instead of zero:
Why duration outranks depth for real people
A recovery that arrives in year fifteen is arithmetic, not consolation, for someone who needed the money in year three. Time under water is where a portfolio's risk statistics meet a person's actual horizon, and the mismatch between the two is the mechanism behind most abandoned plans.
That is an observation about how the numbers work, not advice about how long anyone should hold anything. What the measurement gives you is a clear-eyed record of what a given strategy has historically demanded in patience — a fact, available in advance, rather than a discovery made mid-decline.
Try it now
- The full history of a broad fund is below. Find the peak before the 2008 decline, Measure down to the low that followed, and note both the depth and the number of bars.
- Now measure the part nobody quotes: from that same peak forward to the first bar that closes above it. Count the months. Depth is the number in the headline; this is the number the holder actually lived through.
- Do both measurements again on a technology-heavy fund through the previous cycle — its 2000 peak is on the chart below. Compare the two durations and write one neutral sentence about what differed: depth, duration, or both.