Frequencies for first 10,000 rows of repeac variable in natl1991 dataset : Repeat | C-section | Freq. Percent Cum. ------------+----------------------------------- 1 | 827 8.27 8.27 2 | 9,157 91.57 99.84 9 | 16 0.16 100.00 ------------+----------------------------------- Total | 10,000 100.00 by Jean Roth , jroth@nber.org , 22 Dec 2015