Frequencies for first 10,000 rows of ob_srvc_cd variable in pos2012 dataset :

   Services |
  Provided: |
 Obstetrics |      Freq.     Percent        Cum.
------------+-----------------------------------
          . |      8,606       86.06       86.06
          0 |        774        7.74       93.80
          1 |        555        5.55       99.35
          2 |         37        0.37       99.72
          3 |         28        0.28      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 26 Jan 2016