Frequencies for first 10,000 rows of nprevisrflg variable in natl1982 dataset :

      Total |
  Number of |
   Prenatal |
 Visits (by |
State) flag |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |          1        0.01        0.01
          1 |      9,999       99.99      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 3 Jan 2016