Hacker News User Base Changed?

There are lots of references on Hacker news to the fact that the "good old days" are gone and that the character of the site has changed since it started.  The visualization above was based on a sample of users that posted on the site in recent times.  The data was gathered by iterating over the first 1000 pages and gleaning a list of user names.  The users ages were then checked and are plotted above.

The Chart's Meaning
Note that the chart does not represent the number of posts by a given user, it is just a list of distinct users with their start dates grouped in monthly buckets.  I suppose that the shape of the graph makes sense - folks sign up so that they can post, and older users drift away and cease posting at some point.  The chart does indicate that - as of a few days ago - a a given user who posted was more likely to be someone who signed up in the last year or two than a veteran.

Scraping the Data
I used Ruby and Hpricot (still missing you _why) to parse the site and Active Record to store the list of users in a MySQL database.  I use ActiveRecord outside of rails rather frequently.  It does great straightforward object to relational mapping - and even an arbitrary query is returned as an object that can be manipulated.