Frequencies for first 10,000 rows of musculo variable in natl1989 dataset :

      Other |
musculoskel |
etal/integu |
     mental |
  anomalies |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         25        0.25        0.25
          2 |      9,738       97.38       97.63
          9 |        237        2.37      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 3 Jan 2016