You have to know the distribution of user join dates for this to be meaningful at all. If there are 10x as many users who joined in 2010 as there are those tha

You have to know the distribution of user join dates for this to be meaningful at all. If there are 10x as many users who joined in 2010 as there are those that joined in 2007, then this graph implies that more veteran users are more likely to post.