How Digg Works - or - When to Submit Your Articles

Social bookmark sites can be great to find articles to read when you are at leisure or bored. They are also a great way to promote your website and attract traffic. This article is about how to promote an article at a social bookmark site.

Digg is one of the most popular social news sites and it has been scientifically studied often over the last years. I looked through some articles and found many studies that talk about social information processing and social recommendation with special attention dedicated to digg. From the articles many useful and interesting details about the dynamics of digg can be learned. This includes how article promotion works and when to submit an article at digg.

On Digg, anyone with a free account can submit links and stories, vote, and comment on submitted links and stories. Voting stories up and down is called digging and burying. Many stories get submitted every day, but only few appear on the front page. A newly submitted story first goes to the upcoming stories section, displayed in reverse chronological order of submission time. If the story accumulates enough votes shortly and meets promotion requirements, it will be moderated as a popular story and promoted to the front page, becoming more visible, otherwise the story gets pushed down in upcoming stories.


In order to find out how to get most visibility for your submitted story, lets start with the demographics of digg. This can give us clues about what people at digg might be interested in. According to Alexa, the typical digg user is a US-American college-educated male between 25 and 34 without children who visits from home.

What are US American guys between 25 and 34 most interested in? My guess is, probably girls, entertainment, and games. By the way, did I mention the nude geek chick on the bottom of this page?

Now to some of the studies I found.

What Digg does is called by some social information filtering. Somebody recommends a story, the story gets promoted over networks of related people, so that if one person likes an article a friend picks it up[1]. In initial voting patterns the more unrelated voters are the more likely it is that there will be more diggs[2]. Makes immediate sense to me.

I found many clear conclusions and graphs in the article Measurement and Analysis of an Online Content Voting Network: A Case Study of Digg by Yingwu Zhu. In the following two paragraphs I present a short summary of this paper.

The mechanisms of article promotion to the front page are essential to the success of digg and they do not make them public. This secrecy helps them protect against spam. Yingwu Zhu investigated promotion and found there is a cutoff by diggs. In his study, all popular stories received 15 diggs or more before promotion. However, cutoff is not the only factor. He found one upcoming story which received about 1900 diggs without getting promoted. He concluded there was a content censorship on advertisement, phishing articles and articles perceived offensive to Digg.

For both upcoming and promoted stories, digging frequency diminishes over time, however promoted stories get digged much more. Upcoming stories get nearly forgotten after 1 day, while promoted stories can come up again after one, two, or three days. After 1 day stories have very low probability of getting promoted. Highest chances are within the first hours (7 or 8 hours it seems). Zhu found that 88 percent of articles get promotion at age 1 day or younger.

Also a great study on digg can be found in the article Predicting the popularity of online content by Gabor Szabo and Bernardo A. Huberman. The graph below is taken from this article. It shows daily and weekly cycles in the rates of digging activity. The three curves show diggs, submissions, and promotions, which have been brought to similar scales by multiplication with powers of ten. The data come from one week, days are Monday to Sunday.


You can see when there is most activity at digg over the week and over the day (before and after lunch?). I think it becomes clear from the graph that article submission does not have equal changes on all days. In fact it seems that submission on Tuesday has highest chances of success, because of the better relation of promotions with respect to submissions. It has to repeated however that data in the study are based on only one week and that there may be differences depending on which week you look at. This answers partly the question of what's the best time to submit an article.

Now to the best hour. The hour of when best to submit an article does not really become clear from above graph. I took the graph below from Szabo and Huberman's article. I simplified it to show average diggs of submitted article by promotion time (measured 24 hours after promotion).


Notice the difference between submission time and promotion to the front page. I didn't find a graph showing diggs by submission time. But I still think that you can get a basic idea on when to submit an article if you bear in mind that most articles get promoted within the first few hours of submission.

There are two peaks during the day, one around 6 am, the other one at about 8 pm. This means that if your articles get promoted at these times you can get many diggs and consequently you can hope for many visitors. For submission this means that you should try to submit a few hours earlier. (Please note that the times mentioned throughout this post are in Pacific Standard Time, PST.)

That's all. I'd be happy to read your comments. And please digg me at the right time ;).