Cumulative distribution of planet period ratio (left) and inner planet period (right). The black solid line represents the observations, whereas the red and blue lines show the results from the migration and the in-situ scenarios, respectively. The solid lines are the result of D1 in all four panels. Dashed lines give the results of D2 in panels a and b, and D3 in panels c and d, respectively. Vertical lines mark the 3:2 and 2:1 MMRs.