Slide 12 of 50

The cumulative number is the total number of impacts, formed over all time (for all sizes up to a given size or in certain size range), in a certain area of the surface. [See R.A.F. Grieve and M.R. Dence, The Terrestrial Cratering Record II: The Crater Production Rate, Icarus, Vol. 38, 1979, pp 230-242.]