I recently noticed that Niall now has more twitter followers than Harry, so I wanted to see if this was reflected in their popularity as characters in fanworks, so I looked at their AO3 character tags. Nope. Top graph shows raw numbers per year for each character tag (I used the advance Work Search while logged in). Bottom graph shows the same as a percent of all AO3 fanworks updated that year.
AO3′s overall popularity has changed dramatically, so the normalized version may be less useful.
A limitation on using character tags is that I think a lot of people just tag for everyone who appears, not just the main character(s). Plus Louis being the second most popular probably is due to the prevalence of Harry/Louis.














