Frequencies for first 10,000 rows of opthmlgy_srgry_sw variable in pos1999 dataset :

      spec: |
opthamology |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      9,372       93.72       93.72
          N |        298        2.98       96.70
          Y |        330        3.30      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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