Frequencies for tow_veh variable in vehnit dataset :

      TOWED |
   TRAILING |
       UNIT |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      1,205       90.74       90.74
          1 |        114        8.58       99.32
          2 |          4        0.30       99.62
          3 |          1        0.08       99.70
          5 |          1        0.08       99.77
          9 |          3        0.23      100.00
------------+-----------------------------------
      Total |      1,328      100.00

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