Why Yesterday's Winning Fund Manager Rarely Repeats
A fund's strong past track record has shown surprisingly little reliable power to predict its future performance.
A natural response to the previous two chapters' arithmetic is to try to simply identify, in advance, which specific active managers will be among the rare ones who beat the market after costs. Bogle's own extensive review of the mutual fund industry's actual track record finds this approach far less reliable than most investors assume.
The specific, well-documented pattern: funds that top the performance rankings in one multi-year period are, on average, no more likely than randomly chosen funds to be among the top performers in the following period — a genuinely different finding than the common intuition that a fund's own recent track record is meaningful evidence of the manager's skill continuing forward.
This doesn't mean skill doesn't exist at all in fund management, or that every top performer's success was purely luck — it means that identifying which top performers had genuine, repeatable skill versus which simply had a lucky run, in advance, has proven remarkably difficult even for professional fund selectors with access to far more information than an individual investor.
| Common assumption | What Bogle's review of the data found |
|---|---|
| A fund's strong 5-year track record predicts continued outperformance | Top performers in one period are, on average, no more likely than chance to repeat in the next |
| Picking last decade's best fund is a sound forward-looking strategy | Past performance data, by itself, has shown little reliable predictive power for future results |
A fund that outperforms for five years running could be run by a genuinely skilled manager, or could simply be one of many funds where, by ordinary statistical variation alone, some are bound to look exceptional over any given stretch purely by chance.
With thousands of funds competing, some multi-year outperformance is a near-certainty to occur somewhere in the population even if every manager had identical, average skill — which is exactly why a single strong track record, on its own, is weak evidence of genuine, repeatable skill.
If distinguishing genuine, repeatable skill from a lucky run is this difficult even with the benefit of hindsight and professional-grade analysis, betting real savings on correctly identifying the next such manager in advance is a much harder task than it appears — which is exactly the gap the index-fund alternative, covered later in this course, is designed to sidestep entirely rather than try to solve.
- Funds that top the rankings in one period are, on average, no more likely than chance to top them again in the next period.
- A strong track record can reflect genuine skill or simply ordinary statistical variation across a large population of funds — the two are hard to tell apart in advance.
- Professional fund selectors, with far more information than an individual investor, have not reliably solved this problem either.
- This difficulty is exactly what motivates the index-fund alternative covered later in this course — sidestepping the manager-selection problem rather than trying to solve it.