Lots of people have already replied to this topic, but I think that this piece that I posted on another pony site a few weeks ago might still be able to contribute. I have seen many people using the compete.com number, and I talk about some of the shortcomings with Compete in here. I'll try to update this a bit though to make it less ridiculous...
Ok, I know that this is super long, but there is really no other way for me to do this. Please skip to the end of this if you just want some kind of number estimate for the population of bronies. The section is labeled.
I discovered the show before I knew about bronies. I initially found out about the brony community when I was trying to find Rainbow Dash wallpaper for my computer. Since I cam from a statistics background, the first thing that I tried to do was to figure out how many bronies are out there.
Using Compete's Numbers
Like many people in this thread, I started with the numbers from compete.com. Here are some compete.com numbers for a couple of the central sites:
http://siteanalytics...striadaily.com/
http://siteanalytics.../mlp.wikia.com/
http://siteanalytics...s.memebase.com/
(Compete.com is down right now, but it should be back within a few hours. I really wish I had pasted in the numbers I had.)
The Problems with The Numbers
These are big numbers, but there are actually a few problems with these numbers.
The first problem with the compete.com numbers is that they are only estimates. These are not the accurate number of unique visitors to each website. Compete gets these estimates by monitoring the online behavior of a couple million *US-only* internet users. So these estimates totally exclude the rest of the world.
The second problem with compete's numbers is that they only estimate unique visitors. Unique visitors is a fuzzy concept to estimate because it is actually counting "unique" IP addresses. There are a few problems with this. IP addresses only loosely correlate with the number of visitors that a website gets.
Users connecting to the Internet from college or high school are typically only represented by one IP address or no more than a handful. A family of bronies would also only count as one IP address.
Since we are looking at the brony community, this is especially important. Most bronies are still in high school or college. This means that they are likely to connect to these sites from some type of campus or a home (with potentially more than one brony). This suggests that Compete.com may be dramatically underestimating the population of bronies on the Internet.
One thing to think about when you are estimating the number of bronies is that Equestria Daily gets about 500,000 page views per day. I doubt that kind of traffic could be generated by only 80,000 individuals.
We can look at some other things when trying to estimate the population of bronies as well.
Youtube Videos
Youtube video hits is another avenue to trying to estimate the population of bronies. Quite a few of the popular videos on youtube have several hundred thousand or even over a million views (links excluded because I don't want them to embed):
Flutterwonder ~= 500,000
Equestria Girls ~= 1.3 million
Rainbow Dash (You're Gonna go far kid) ~= 2 million
Of course, you can watch youtube videos more than once, but still, these kind of large numbers suggest that the brony community that is active online is pretty large.
Estimating the Population
Using all of this information, we can try to come up with a very rough estimate for the total brony population.
Outside of the U.S. Friendship is magic has some popularity in Europe and other parts of the world. To be conservative, we will just look at Europe.
We can make the assumption that the percentage of European internet users that are bronies is similar to the percentage of the American internet population. This means that we can multiply the Compete estimates by 2.6 to (roughly) include the European bronies. ([European internet users + us internet users] / us internet users. Data from Wolfram Alpha.)
This gives us a number of between roughly 200,000 to 500,000 unique visitors depending on the amount of overlap of users that visit more than one of the 3 major sites I linked above. As I mentioned earlier though, unique visitors is probably an underestimate of the actual number of bronies.
I have read in a few places that the ratio of actual users to unique visitors is between 1.3 and 1.7. (Counted by counting site cookies or examining browser differences.) If we make this slight correction, then we can adjust our population estimate range to 260,000 on the low end and to 850,000 on the high end.
The 260,000 to 850,000 range is probably a safe estimate for the brony population. While there may be some overlap between the visitors of the major fan sites, I think that the upper end of that range is probably more likely. My reason for thinking that is that bronies tend to be much younger than the overall population, and therefore they are more likely to share an ip address but only be counted as a single "unique visitor".
More Stuff to Think About
Of course, the parents that watch this show with their children and buy their kids toys is probably a little larger than the actual brony community.
And, the "silent" bronies that watch the show but rarely or never visit the fansites could easily be 2 or 3 times the number of *active* bronies. Just thinking about myself, if I had never went looking for wallpaper, then I may have never have discovered the community.
Of course, it is also important to keep in mind that the number of bronies out there in the wild is actually increasing as time goes on. Just take a look at this:
http://www.google.co...date=all&sort=0
http://www.google.co...date=all&sort=0
Google trend charts give you an idea of the "trending line" in the number of people that are actively searching for a topic. Just look at that run up in popularity for the show and the similar run up in popularity for the term "brony" which didn't even exist before 2010.
On Demographics
Well, you can get demographics estimates for the major sites from Alexa.com. (Only the information for the major sites is accurate, because Alexa needs a *lot* of data to make their estimates.) I think that EQD is basically the core of the fanbase at this point, so I will link to its profile.
http://www.alexa.com...estriadaily.com
To get the demographic info, just click a link and then click the audience tab. It turns out that there are slightly more females than males.
I know that males tend to be dramatically overrepresented in polls, but maybe the reason for this is that they are, for whatever reason, more likely to want to answer brony polls?
Edit: Ummmmm..... Mods? Please don't ban me for getting a little carried away here......