Last year, Nature compiled the 100 most cited scientific papers. The top paper that deals with method evaluation is Bland and Altman’s paper from the Lancet in 1986. Number 29 on the all-time list, this paper is the source for the Bland-Altman (or difference) plot and associated statistics. One of the reasons that this paper is so popular is that is makes a complex topic simple. What could be easier than to plot differences. A paper in Clinical Chemistry showed that in spite of the popularity of the Bland-Altman method, it was not used as much as one might expect (only about a third of papers used it).