Oh, that's easy. Sites like Compete don't know shit about shit. For further details:

http://blog.reddit.com/2010/07/experts-misunderestimate-our-...

The description seems like it's for another website:

StumbleUpon

San Francisco, California United States stumbleupon.com We provide technical consulting, training, and information services to build capacity, share knowledge, and support local government in the implementation of sustainable development at the local level. Our basic premise is that locally designed initiatives can provide an effective and cost-efficient way to achieve local, national, and global sustainability objectives. ICLEI was founded in 1990 as the International Council for Local Environmental Initiatives. The council was established when more than 200 local governments from 43 countries convened at our inaugural conference, the World Congress of Local Governments for a Sustainable Future, at the United Nations in New York.

Neither http://www.alexa.com/siteinfo/stumbleupon.com nor http://www.quantcast.com/stumbleupon.com show anything nearly as dramatic...

SU's own recent blog post about their traffic: http://www.stumbleupon.com/sublog/20-million-stumblers/

I wonder if there is a correlation between the increase of traffic and the launching of their link shortener http://su.pr?

If I remember correctly there was a minor bump with the release of su.pr, but the recent growth has been correlated mainly with their mobile applications.

su.pr was launched in 2009, so I don't think there's a direct correlation. Just a lot of users and really good recommendation algorithms. They've been also steadily improving their mobile and ipad apps.

I'm not sure of the accuracy of complete's site analytics.

I'm absolutely sure they're woefully inaccurate. We've compared their data to our own GA data and their numbers are so far off it's laughable - or it would be if we weren't spending an arm and a leg to get them.

I have compared Compete's numbers to actual data from about 150 sites.

On that sample the numbers were never higher than actual and on average the Compete numbers were 2-3x lower than the actual numbers.

So I have used it as a reasonable estimate for half of the traffic a site sees. Although I may be placing my foot in my mouth because the stats for HN don't quite seem accurate: http://siteanalytics.compete.com/news.ycombinator.com/

Some of my sites receive 10 to 100 times more traffic than reported by compete.

Are they sites with less than 20,000 uniques per month? I've found those to be the outliers in my data set. They're wildly off on "low" traffic sites but have been a decent yardstick for sites getting more than 20k uniques in my limited experience.

No, more like 50,000-150,000 (depending on the month).

compete is a trainwreck. i wouldn't trust it, even for comparative analysis, at least based on the sites i've sampled

Would you mind expanding on this? Why do you think is a train wreck and where would you recommend to check for analytics?

Thanks!

Google trends shows a recent uptick also, particularly in Ireland:

http://www.google.com/trends?q=stumbleupon&geo=irl&s...

You can also measure websites in google trends:

http://trends.google.com/websites?q=stumbleupon.com&geo=...

They don't have the data for Ireland, but there's no uptick here for "All Regions".

Weird -- today my 68 year old mother asked me if I had heard of it and that she loved it. She mentioned it was great for foodie sites. The compete numbers may be exaggerated but it seems to strike a chord across a broad audience.

I wonder who the demographics are of the people who use StumpleUpon. I don't know anyone who uses it, and no one ever really talks about it, but somehow they manage to put up these huge traffic numbers that keep growing. It would just be interesting to see how they're growing outside of the standard echo chamber.

I think it's just the 'ordinary' people. Analytics tells me stumblers spend little time on my site, and my anime articles do the best (as compared to the philosophy or programming articles), so...

Well, they are definately not stumbling