Not only this but also the number of votes from users who were active years ago is also a very interesting metric to see. No doubt HN audience has changed over

Not only this but also the number of votes from users who were active years ago is also a very interesting metric to see. No doubt HN audience has changed over the years and votes from original users are diluted by votes from new comers. It won't be easy to do but one could aggregate "favorites" from all users on a daily basis and only count the votes from users with an old registered date.