Frequencies for ptrailer variable in parkwork dataset :

    vehicle |
   trailing |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      1,000       88.26       88.26
          1 |        122       10.77       99.03
          2 |          5        0.44       99.47
          4 |          2        0.18       99.65
          5 |          1        0.09       99.74
          6 |          2        0.18       99.91
          9 |          1        0.09      100.00
------------+-----------------------------------
      Total |      1,133      100.00

by Jean Roth , jroth@nber.org , 22 Oct 2016