Check out the graph (courtesy Lookout) below. It shows the increase in number of apps in Apple and Android markets over the last 6 months.
From the slopes of the lines, Apple app store is clearly growing at a faster pace. However, if you consider the percentages, Android app store is growing faster!! What do you believe?
By connecting two points with a straight line one should not make inferences about the growth rates. If we consider that the Android market is growing faster because it has more than doubled the size in the last 6 months, can we infer that this growth rate will remain constant? This means that the straight line will not be straight any more and there will be exponential growth! But from this graph (2 points) I don’t see how anyone can make that inference. Anyway, that’s what precisely tech bloggers are doing. See the original report and then CNET and Slashgear.
Update: Here is a very simple way of understanding the fallacy. If Android market is growing faster than Apple store, you should see it overtaking Apple store in future. If, however, you extend these two lines on the graph to future, you will never find them intersecting! In other words, Android market will never overtake Apple store at this growth rate.