Frequencies for first 10,000 rows of cityres variable in natl1981 dataset :

  NCHS City |
         of |
  Residence |      Freq.     Percent        Cum.
------------+-----------------------------------
        021 |        811        8.11        8.11
        030 |          3        0.03        8.14
        048 |        383        3.83       11.97
        054 |        432        4.32       16.29
        057 |        357        3.57       19.86
        999 |      8,013       80.13       99.99
        ZZZ |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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