Stats › Concentration and breadth › Index turnover
The average S&P 500 company lasts about 15 years
| Measure | Figure |
|---|---|
| Average tenure in the index | about 15 years |
| Turnover across a 30 year hold | about twice |
| Companies actually in the 500 | 503 |
| Largest single cause of exit | acquisition |
| Global deal value, 2025 | $4.8 trillion |
Acquisition is the largest single cause of exit, the same activity that has halved the number of US public companies since 1996. Sources: Apollo Academy, citing Innosight corporate longevity research, and Bain & Company for 2025 deal value.
Membership of the S&P 500 is not permanent. Companies join by growing into the size, liquidity and earnings tests and leave when they are bought or shrink out. The average stay is about fifteen years, so a thirty year holding turns over roughly twice.
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