Frequencies for first 10,000 rows of cityres variable in natl1971 dataset :

  NCHS City |
         of |
  Residence |      Freq.     Percent        Cum.
------------+-----------------------------------
        012 |          3        0.03        0.03
        021 |        989        9.89        9.92
        075 |          1        0.01        9.93
        078 |          2        0.02        9.95
        096 |          1        0.01        9.96
        156 |          1        0.01        9.97
        999 |      9,003       90.03      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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