Frequencies for first 10,000 rows of opthmlgy_srgry_sw variable in pos1991 dataset :

      spec: |
opthamology |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      9,683       96.83       96.83
          N |        100        1.00       97.83
          Y |        217        2.17      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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