Why You Shouldn’t Use Alexa Traffic StatisticsBy Collin Maessen on comment
Watts is known for using Alexa web traffic statistics to show how well his website is doing compared to other blogs. Often to boast he’s doing far better than for example Skeptical Science or Real Climate.
Via the comment section of WottsUpWithThat the user @vitaminCSS pointed to a tweet where he joked around a bit about the graphs in response to Watts latest usage of Alexa data. Because I saw his comment I responded to his tweet saying that “Alexa is notoriously unreliable with the type of statistics it gives. You can’t do any comparisons with it.”
It was just me giving an opinion on how inaccurate the Alexa data is and that you shouldn’t use it. Watts did respond to my remark, and before I address his response to me I’ll explain why I think Alexa data is unreliable.
One of the reasons is that I graduated from university with a diploma in Information Technology. It makes me a software engineer and it allows me to use the protected title of Engineer in my country. I work for a software development company where we develop and maintain for example complex web retail software. Almost always coupled to online campaign and tracking software. This makes me well aware of the limitations of certain technologies or products.
That’s why I know that Alexa data is basically worthless if you’re trying to do any serious analysis of visitor numbers to websites. You just don’t use it as you will almost always get something that isn’t remotely close to reality (although some businesses do use this data).
What you need to know about how Alexa gathers their data is that they are dependent on users installing their toolbar (or a toolbar that passes information to Alexa). It’s this toolbar that provides data for their statistics. This makes you reliant on visitors to your site having this toolbar installed for their visit to be counted by Alexa. It’s something they state on their website:
Alexa’s traffic estimates are based on a diverse sample of millions of worldwide internet users using thousands of different types of toolbars and add-ons for Google Chrome, Firefox, and Internet Explorer.
This can introduce big biases in the data collected for websites. Something they try to correct for but it’s also something they say they can’t fully correct for (emphasis mine):
Alexa’s ranking methodology corrects for a large number of potential biases in our sample and calculates the ranks accordingly. We normalize based on the geographic location of site visitors. We correct for biases in the demographic distribution of site visitors. We correct for potential biases in the data collected from all the various browser extensions to better represent those types of site visitors who might not be in Alexa’s measurement panel. However, biases still exist, and to the extent that our sample of users differs from the set of all internet users, our traffic estimates may over- or under-estimate the actual traffic to any particular site.
This means that demographic, used browsers, and even the country your users are from matter in regards the statistics about your website. It’s why you should only put any serious stock into statistics derived from direct measurement of visitors by the website itself (and event then you need to know about weaknesses and how to interpret data). Indirect measurements can give you a hint, but should be taken with a big grain of salt. As they tend to give you the wrong answer about visitors and how they end up on sites.
All this is known in the industry. That’s why for websites you always use your own web statistics software. It’s the reason I use multiple types for my site, each with a specific goal. They show that the statistics Alexa has for my website underestimate and overestimate statistics. Some do get close but they tend to vary a lot, often I’ve seen statistics that don’t make any sense compared to the actual data.
Currently the statistics for search engine keywords are the ones that are hilariously wrong. Alexa says that “heyruka” is the most common search term visitors end up with on my website and estimates it at 64%. The actual number is 1%.
The other numbers like “pages per visitors” and “time on website” are off between 20% and 50%. That’s significant.
Alexa seems to suggest that WUWT is indeed more visited than for example Skeptical Science, but with the inherent inaccuracies you don’t know this for sure. You can only determine this if Watts and Cook would publicly release the direct traffic measurements (although they would have to be in a comparable format and measure the right metrics to make a good comparison).
Watts should know this considering how often it was pointed out to him that Alexa isn’t reliable. He should also known this because WordPress can and does track visitor statistics (if you host your own WordPress blog you need the JetPack plugin to do this, but it is standard functionality for a WordPress.com hosted blog).
He also uses sitemeter, which is a direct measurement of traffic on his website (it’s mentioned in the sidebar of his website). And if you look at the code of his blog you’ll notice that he’s also using Quantcast.
If you compare the Alexa statistics with his Quantcast statistics you’ll notice Alexa seems to be actually underestimating his statistics based on the page views per visitor (I don’t trust the Sitemeter statistics as it deviates too much and there are complaints that Sitemeter undercounts visits and page hits). Although I don’t know if Alexa is overestimating or underestimating the total visitors to his site:
|Daily Pageviews per Visitor||3.27||1.4||4.6|
|Average Visit Length (mm:ss)||8:32||0:19||–|
That’s a similar deviation that I get with my website, despite that Alexa should be more accurate with more visitors. And as far as I can tell from his website code he isn’t using the Alexa Certified Site Metrics. If he was using that it would mean Alexa was tracking his actual visitor statistics (it uses a script on the website to measure traffic).
But he does have a WUWT toolbar listed in the sidebar of his website, which is a custom Alexa Toolbar. If enough of his visitors have that toolbar installed it has the potential to introduce a bias into the Alexa statistics.
Alexa has a tendency to overestimate and underestimate traffic to websites, it’s just too unreliable to do any meaningful comparisons between sites with.
All this is why I said what I did, and this is how Watts responded when he noticed the tweet:
For one his response is an ad hominem attack, he went after me personally instead of after the point I made. As I’ve said I do my utmost to be civil, so I do not appreciate it when people do this. Especially when Watts says he wants to be treated civilly.
It also misrepresents what my point was. I was talking about the Alexa data as that is what isn’t reliable. I have no reason to believe that the direct measurements from TIME, WordPress or Quantcast aren’t accurate (I’m running a test with Quantcast).
I’m also not “110% anti WUWT.” I sometimes agree with him on certain points and I’ve defended him in the past. One example of this was when Greg Laden published an article that in my opinion was unfair to Watts. Also Laden wasn’t helping with how he was responding to critics. The one interaction I had with Laden about this on Twitter led to him blocking me.
Because of that my response to Watts was a bit snarky with me stating:
Nice comeback, a personal attack… I work in IT, that’s why I said what I did about Alexa.
Even after this hint that I might have the relevant expertise he just dismissed me and ended up blocking me. I have no idea why this was such a sensitive topic to him that he didn’t even consider that I might have a valid point.
And another indication that Alexa statistics are not reliable is the jump in WUWT traffic according to Alexa. A WUWT post on that jump was the starting point of this whole discussion.
This Alexa jump is not visible in the number of comments, in Sitemeter and in Quantcast. Thus the Alexa jump is likely artificial.
It would be logical if Anthony Watts would know that the jump is artificial, he can have a look at his WordPress statistics after all. I would suspect that that is the reason he is so sensitive about the topic.
For detail see my latest post Anthony Watts calls inhomogeneity in his web traffic a success.
True, it indeed was the starting point as I acknowledge at the start of this post. But it was just a symptom of how unreliable Alexa traffic statistics are and the problems you get when you use it. So I only spent attention on the inherent problems with Alexa statistics.
The numbers we have from direct measurements indeed don’t indicate a jump in the amount of traffic to his website. For example my website went from being ranked at 21 million to being ranked at 3.2 million this year. But I claim bullshit on how and when this happened according to Alexa. My traffic has increased but those graphs don’t match at all with the Alexa statistics.
Considering the amount of times it was pointed out to him that Alexa is not reliable he should logically know this. But I refrain from speculating on motive as we can’t really know what is going on in his head.
OK, so the statistics are well over my head,
but I do find it ironic that Watts who’s never seen a climate statistic he trusts –
thinks that a counter that needs many adjustments:
“Alexa’s ranking methodology corrects for a large number of potential biases in our sample and calculates the ranks accordingly. We normalize based on the geographic location of site visitors. We correct for biases in the demographic distribution of site visitors. We correct for potential biases in the data collected from all the various browser extensions to better represent those types of site visitors who might not be in Alexa’s measurement panel.”
and that even warn: “However, biases still exist.” Is just fine.
No matter, if it tells Watts’ what he wants to hear, it’s accepted as fact with amazing alacrity.
Good comment, I have added it to my post: “Anthony Watts calls inhomogeneity in his web traffic a success“. Nicely fits to my blog that is mainly about temperature adjustments (homogenization).
Then you might like my blog post ‘This Is Why You Shouldn’t Use Alexa‘ better. It uses data from HotWhopper and my website to illustrate the problems with how Alexa gathers its data and generates its statistics. Which makes it a lot less abstract compared to this post.
Useful discussion but from what I can see every technology we have at the moment to benchmark our sites and those we deal with is flawed. Google analytics and Domain Rank certainly have their issues which negatively impact some while being exploited by others to show higher than realistic results. It’s also amusing to see people still quoting page rank so long after it was last updated and comparing against newer sites for low or zero PR.
Google’s PageRank (which I assume you meant by Domain Rank) is not exactly a benchmark tool. It’s Google’s algorithm for ranking websites in their search engine results. It can give you some information about what Google’s search engine thinks about your website but I wouldn’t use it to determine how well a website is doing. Way too many variables in there that you have no idea about what their values are or how they’re used.
Google Analytics is basically reliable, it measures after all what you tell it measure and within its technical limitations it does this accurately. It can only be “exploited” if you let it measure more than it should measure or feed it data. But that’s not unique to Google Analytics, all analytics software can be abused in that way. I have my Google Analytics set up so that it only tracks visitors to my website and not for example me. I know what I’m doing on the site, I’m far more interested in what actual visitors do.
Flawed is not the word I would use for all analytics software. That I reserve for tools that actually have big issues caused by how they work or collect their data, like Alexa.