Rotation period P_min vs. α for all stars with two detected periods. The colors represent different temperature bins, the dashed black line marks the detection limit. The relative shear α grows towards longer rotation periods. More than 75% of all stars with detected period P₁ exhibit a second period P₂, and lie above the detection limit. This trend cannot be broken by the 5505 stars with only one detected period, because most of the missing stars lie above the upper limit α_max = 0.3.