Frequencies for first 10,000 rows of cityres variable in natl1980 dataset :

  NCHS City |
         of |
  Residence |      Freq.     Percent        Cum.
------------+-----------------------------------
        003 |          1        0.01        0.01
        009 |          1        0.01        0.02
        021 |        843        8.43        8.45
        030 |          2        0.02        8.47
        048 |        392        3.92       12.39
        054 |        358        3.58       15.97
        057 |        426        4.26       20.23
        081 |          1        0.01       20.24
        096 |          1        0.01       20.25
        999 |      7,974       79.74       99.99
        ZZZ |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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