Frequencies for first 10,000 rows of cityres variable in natl1978 dataset :

  NCHS City |
         of |
  Residence |      Freq.     Percent        Cum.
------------+-----------------------------------
        003 |          1        0.01        0.01
        021 |        750        7.50        7.51
        084 |          1        0.01        7.52
        096 |          1        0.01        7.53
        999 |      9,246       92.46       99.99
        ZZZ |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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