# Designing a fair user recommendation system

In this chapter, we design a *fair* user recommendation system for Mastodon, in step-by-step style.

First of all, we have to avoid the oldies effect. We can choose weekly, monthly, or other criteria with some finite duration.

Second, to avoid the shrink-wrap effect, we have better to use the number of boosts, rather than the numer of followers.

Now we find that, the weekly number of boosts is a *fair* criteria to recommend the users.

And one more thing, a reverse *unfair* criteria is *fair*. For example, we can imagine a rule that the user who has more than 100 followers is not recommended. This rule can be combinated with the weekly number of boosts criteria, which brings some additional *fairness*.

Now we get a design of a *fair* user recommendation system for Mastodon. Implementation is expected.


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