Frequencies for first 10,000 rows of cityres variable in natl1972 dataset :

  NCHS City |
         of |
  Residence |      Freq.     Percent        Cum.
------------+-----------------------------------
        021 |        885        8.85        8.85
        027 |          1        0.01        8.86
        066 |          3        0.03        8.89
        069 |          2        0.02        8.91
        075 |          2        0.02        8.93
        102 |          1        0.01        8.94
        156 |          1        0.01        8.95
        180 |          1        0.01        8.96
        999 |      9,103       91.03       99.99
        ZZZ |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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