The Trinity study was about an individual's savings. A group, like a pension fund, has different requirements. The reason is mortality. Let's say an individu

The Trinity study was about an individual's savings. A group, like a pension fund, has different requirements. The reason is mortality. Let's say an individual has a 20% chance of reaching age 90. They are not willing to take the risk of being 90 and broke, so they need to save for ages 90-95. With a large group of people, mortality is much more predictable. The ones that die early collect less, so the lucky few that live a long time can collect more. To learn more about this, the term to look for is "mortality credit".