Frequencies for first 10,000 rows of pre4000 variable in linkco1991us_num dataset :

   Previous |
     infant |
4000+ grams |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         39        0.39        0.39
          2 |      9,673       96.73       97.12
          8 |          9        0.09       97.21
          9 |        279        2.79      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 22 Dec 2015