Relation in several young star-forming regions between disk fraction and their age. The fraction of Class I + Class F + Class II disks is shown as filled dots, while the fraction of Class III disks is shown as crosses. Each star-forming region is color-coded according to the legend. The filled triangles in the lower panel represent the lower limits of the debris disk fraction. The blue line represents the fitting of the fraction of Class I + Class F + Class II disks, with a slope of −0.32 ± 0.11.