Period-mass diagram for planets in single (red circles) and multiple systems (blue circles). The horizontal black line divides the sample into high- and low-mass regimes using a cutoff of 0.1258 M_Jup (40 M_⊕), while the vertical black line at P = 100 d marks the position of the arithmetic mean of the distribution in orbital periods. The information showed for each quadrant is the number of planets in multiple, N_m, and single systems, N_s, the fraction of planets in multiple systems with respect to the whole sample, f = N_m/(N_m + N_s), the difference ∆ƒ between this ratio and the value computed for the total sample (f_tot = 0.246), and, in parenthesis, the statistical significance p of the differences. No information is offered for the bottom-right quadrant due to the insufficient number of planets.