What if we had a challenge to encourage people to roughly approximate missing birth years for profiles for which they are the manager?
To keep it simple, we could encourage people to add ~ 10 date guesses a day. They could easily find the profiles missing dates by looking in their watchlists and sorting on the birthdate field.
We could provide some quick guide to estimating birthdates based on dates of siblings, children, parents, etc.
It might present a challenge for people with profiles pre-1700, but we could point people to the Pre-1700 Certification Quiz to aid those people.
It would be a start, at least.
How would we go about making this a good, fun challenge for people?