Richard Cunningham has done some interesting analysis of the types of stories that have been popular on Digg over time. The main trend seems to be that tech stories are shrinking rapidly, while things like “offbeat” stories are increasing. It’s pretty clear that Digg is becoming more mainstream, by accident or by design.

Anyway, I don’t want to be too critical, but the stacked graphs that he uses are just horrible. Check out this one which shows the number of popular Digg stories by category (click for bigger):

Stacked graphs do show you how the composition of something changes over time. But it also makes comparisons of trends across categories very difficult. To compare the lifestyle category to the offbeat category, for example, you have to somehow figure out the relative thickness of the two areas and then try to figure out how this varies over time. For mere mortals like me, this is impossible. Much better would be a line chart that allows easy comparison between categories. If you want to examine how the total composition of stories changes over time, give a table or line chart of the percentage of stories in each category. It’s very rare to come across a situation where a stacked chart is a more effective way to communicate information than a simple line or bar chart.

(HT: RWW)