Frequencies for first 10,000 rows of op_tocol variable in natlterr2009 dataset :

  Tocolysis |
        RFP |
602=f_ob_to |
       co R |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      2,449       24.49       24.49
          N |      7,398       73.98       98.47
          U |          2        0.02       98.49
          Y |        151        1.51      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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