Frequencies for first 10,000 rows of rf_ppterm variable in natlterr2012 dataset :

   Previous |
    Preterm |
  Birth RFP |
587=f_rf_pp |
        b R |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      1,163       11.63       11.63
          N |      8,412       84.12       95.75
          U |        335        3.35       99.10
          Y |         90        0.90      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 5 May 2016