Frequencies for first 10,000 rows of prostrat variable in namcs2001 dataset :

   provider |
    stratum |
     marker |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        890        8.90        8.90
          2 |        681        6.81       15.71
          3 |        518        5.18       20.89
          4 |        850        8.50       29.39
          5 |        473        4.73       34.12
          6 |        619        6.19       40.31
          7 |        806        8.06       48.37
          8 |        509        5.09       53.46
          9 |        944        9.44       62.90
         10 |        748        7.48       70.38
         11 |        691        6.91       77.29
         12 |        606        6.06       83.35
         13 |        473        4.73       88.08
         14 |        565        5.65       93.73
         15 |        627        6.27      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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