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

        nhs |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      7,058       70.58       70.58
          1 |      2,878       28.78       99.36
          9 |         64        0.64      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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