Frequencies for first 10,000 rows of pre4000 variable in natl1990 dataset :

   Previous |
     infant |
4000+ grams |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         76        0.76        0.76
          2 |      9,875       98.75       99.51
          8 |          1        0.01       99.52
          9 |         48        0.48      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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