I read an article about how well the Greens did in the local elections recently and got a bit narked. It wasn't about the main thrust of the article (though I'm doubtful how much council election gains for a small party mean in terms of general elections), but rather as a result of a distinctly painful use of the word 'exponential'. In his article, Peter Franklin says 'the Greens grew exponentially — doubling their council seats from 240 to 481'. There are two problems with this. One is you can't tell if growth is exponential from two data points. And the other is that exponential growth does not mean large growth, as seems to be thought here. For something to grow exponentially, each data point (often with this kind of data, separated over a time period such as a week, month, year or as here election period) has to be related to the original value by the exponent of the number of data points. That sounds far more complicated than it really is. If you have ...