Frequencies for first 10,000 rows of mrcntyfips variable in natlterr2003 dataset :

   Mother's |
  County of |
  Residence |
 (FIPS) U;R |      Freq.     Percent        Cum.
------------+-----------------------------------
         21 |        593        5.93        5.93
         25 |        365        3.65        9.58
         31 |        443        4.43       14.01
         97 |        204        2.04       16.05
        113 |        513        5.13       21.18
        127 |      1,123       11.23       32.41
        999 |      6,759       67.59      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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