Peas in a pod: packing. The average sizes (top) and average masses (bottom) of adjacent planets are shown as a function of their orbital period ratios P_j+1 ∕P_j for the underlying population (left), underlying population of detectable planets (middle), and KMPS planets (right). For the underlying population, the position of the inner planet in each pair is in a different colour, showing that the trend is due to those planetary pairs where the inner planet is close to the host star. The black curveshows the Hill stability criterion from Deck et al. (2013). Adjacent planetary pairs on the right side of this curve are Hill stable. Points on the left side are Hill unstable and will probably be removed with longer N-body calculations.