Frequencies for first 10,000 rows of cityres variable in natlterr1998 dataset :

  NCHS City |
         of |
  Residence |      Freq.     Percent        Cum.
------------+-----------------------------------
        000 |          4        0.04        0.04
        999 |      9,991       99.91       99.95
        ZZZ |          5        0.05      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 22 Dec 2015