[diggan]

You can always add classes based on age or membership in the tontine to make it easier.

For example, a tontine of 1000 euros with 10 members, but since the last member is in the age bracket of 20-30 instead of 30-40, they get a smaller annuity than the rest.

The Wikipedia article about tontines mentions this:

> Because younger nominees clearly had a longer life expectancy, the 17th and 18th-century tontines were normally divided into several "classes" by age (typically in bands of 5, 7 or 10 years): each class effectively formed a separate tontine, with the shares of deceased members devolving to fellow-nominees within the same class.

https://en.wikipedia.org/wiki/Tontine