Frequencies for first 10,000 rows of opthmlgy_srgry_sw variable in pos2004 dataset :

      spec: |
opthamology |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      9,098       90.98       90.98
          N |        493        4.93       95.91
          Y |        409        4.09      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 17 May 2017