Frequencies for tow_veh variable in person dataset :

      TOWED |
   TRAILING |
       UNIT |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |        996       77.69       77.69
          9 |         40        3.12       80.81
          . |        246       19.19      100.00
------------+-----------------------------------
      Total |      1,282      100.00

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