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

   Previous |
 Preterm or |
  Small for |
  Gestation |
        RFP |
693=f_urf_p |
   reterm U |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        164        1.64        1.64
          2 |      9,692       96.92       98.56
          9 |        144        1.44      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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