In an attempt to distill the S66 data into a form that can be used for quick side-by-side comparison of different basis sets, we will instead examine average values of E elst , E exch , E ind , and E disp across the entire S66 data set. These averages are not physically meaningful because they do not exemplify any one system; nevertheless, inspection of how the average changes from one basis set to the next provides a simple means to gauge convergence as a function of basis set. This analysis will underscore the fact that not all of the energy components converge in the same way and that some components place different demands on the basis set than others.