Frequencies for first 10,000 rows of nhs variable in accident dataset :

        nhs |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      6,781       67.81       67.81
          1 |      3,184       31.84       99.65
          9 |         35        0.35      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 18 Apr 2016