Frequencies for first 10,000 rows of uld_prepla variable in natl2006 dataset :

   Placenta |
 previa RFP |
715=f_uld_p |
  replace U |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         17        0.17        0.17
          2 |      9,851       98.51       98.68
          9 |        132        1.32      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 22 Dec 2015