I applaud the authors for attempting a new kind of data visualization. However, I find two major flaws in the graph:
1) Because the perimeter of a circle grows as a function of the radius, an arc must grow just to represent the same share. This is misleading, giving an impression of growth where there is none.
2) It is difficult to tell which arcs on one side of the circle go with arcs on other parts of the circle. There is simply too much distance between them to judge accurately which arcs belong to the same time period.
This is misleading, giving an impression of growth where there is none.
But there is growth. Perhaps it's the static percentage based graph that's misleading, I find this graph of more or less the same data rather intriguing:
The market doesn't have to grow by 2 * PI anything. It's just a constant. Since the radius grows linearly, you can map any linearly growing series of data and you'll find it looks good in this presentation format.
Not only that, but the dataset doesn't have even time spacing. In the earlier years, it skipped a couple months, and only recently did it start to do every month.
However, that's not reflected in the visualization, and we're lead to believe that this is sampled with even steps over time.
Keep in mind that this is a tech demo used to show a visualization of someone else's data (W3C in this case). So the author likely cared a lot more for visual appear and demonstrating functionality than for the way the graph might be interpreted.
The growth of the size of an arc is only misleading because the graph naturally draws you to compare different browsers as a percentage of the market.
Since the market has grown basically linearly, the arcs may actually be in direct proportion to the actual number of users, in which case there is very real growth.
The confusion comes when you see growth of absolute terms when the more interesting statistic is what the relative growth is.
Particularly, if one browser's arc remained the same size on each ring you might assume that it is staying the same. It has the same number of users, but it is losing prominence.
Then again, the number of users on the Internet has grown every year, so even if a browser just held its % market share steady, that would mean an increase in quantity of users.
1) Because the perimeter of a circle grows as a function of the radius, an arc must grow just to represent the same share. This is misleading, giving an impression of growth where there is none.
2) It is difficult to tell which arcs on one side of the circle go with arcs on other parts of the circle. There is simply too much distance between them to judge accurately which arcs belong to the same time period.