Frequencies for tow_veh variable in vehnit dataset :

      TOWED |
   TRAILING |
       UNIT |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      1,160       91.19       91.19
          1 |        103        8.10       99.29
          2 |          3        0.24       99.53
          5 |          3        0.24       99.76
          9 |          3        0.24      100.00
------------+-----------------------------------
      Total |      1,272      100.00

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