Frequencies for first 10,000 rows of opthmlgy_srgry_sw variable in pos2007 dataset :

      spec: |
opthamology |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      9,666       96.66       96.66
          N |        126        1.26       97.92
          Y |        208        2.08      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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