Twitter also has its own analytic metrics!

Just turned on the analytics option for the @GeriMedJC account.  Unfortunately, data prior to turning this feature on is not available.  This may be useful going forward to track impressions (times a user is served a tweet in timeline or search results) and engagements (total number of times a user interacts with a tweet).  This is what Twitter analytics had to say about the @GeriMedJC followers in terms of location, gender and who the followers follow: