Frequencies for first 10,000 rows of prostrat variable in namcs1993 dataset :

   provider |
    stratum |
     marker |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      2,053       20.53       20.53
          2 |      3,253       32.53       53.06
          3 |      1,876       18.76       71.82
          4 |      1,667       16.67       88.49
          5 |      1,151       11.51      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 28 Mar 2016