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

        nhs |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      4,601       46.01       46.01
          1 |      4,051       40.51       86.52
          9 |      1,348       13.48      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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