Frequencies for first 10,000 rows of prostrat variable in namcs1997 dataset :

   provider |
    stratum |
     marker |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      1,396       13.96       13.96
          2 |        874        8.74       22.70
          3 |      1,119       11.19       33.89
          4 |      1,178       11.78       45.67
          5 |        334        3.34       49.01
          6 |        529        5.29       54.30
          7 |        260        2.60       56.90
          8 |        931        9.31       66.21
          9 |        599        5.99       72.20
         10 |        252        2.52       74.72
         11 |        592        5.92       80.64
         12 |        300        3.00       83.64
         13 |        427        4.27       87.91
         14 |        387        3.87       91.78
         15 |        822        8.22      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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