Frequencies for first 10,000 rows of nprevisrflg variable in natl1976 dataset :

      Total |
  Number of |
   Prenatal |
 Visits (by |
State) flag |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |         13        0.13        0.13
          1 |      9,987       99.87      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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