Frequencies for first 10,000 rows of stndif13 variable in h84 dataset :

 DIFFICULTY |
STANDING 20 |
    MINUTES |      Freq.     Percent        Cum.
------------+-----------------------------------
         -8 |          3        0.03        0.03
         -1 |      8,973       89.73       89.76
          1 |        315        3.15       92.91
          2 |        326        3.26       96.17
          3 |        193        1.93       98.10
          4 |        190        1.90      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 28 Feb 2018