Here is an answer that was submitted to this question on productmanagementexercises.com. " When I think about what we might want to improve about the birthdays feature, I first think back to why the Birthday's feature exists. I know Facebook's mission is to connect the world and bring it closer together. The feature fits neatly with Facebook's mission statement and since birthdays happen each year, for every user, I imagine Facebook originally launched this feature to grow engagement. That being said, I'd like to improve engagement with the Birthday's feature. I think it's best if we define engagement more specifically so we can measure the success of our improvements. If we think of the birthday feature as an engagement loop we can begin to identify what metrics we care about. 1. User makes their birthday visible to friend 2. User's birthday arrives 3. Friend made aware of user's birthday 4. Friend engages with the birthday user 5. The birthday user engages with the friend 6. Step 2 happens again For step one, I think most users birthday audiences are set to friends by default so we shouldn't focus our time there, and unless time stops we're also ok with not focusing on step 2. I think the feature today already does a decent job of making users aware of users birthdays with notifications etc. I think where we can have the most impact is improving engagement for 4 because many users that are aware of a friends birthday may not engage. A good engagement metric could be to look at the % of users that post on at least one friends wall each day. When I think about who uses this feature I think about a user's relationships to the birthday user. This may be a friend or acquaintance.