Frequencies for first 10,000 rows of optmtrc_srvc_cd variable in pos2009 dataset :

       SRV: |
 OPTOMETRIC |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      8,638       86.38       86.38
          0 |      1,212       12.12       98.50
          1 |         77        0.77       99.27
          2 |         61        0.61       99.88
          3 |         12        0.12      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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