Frequencies for first 10,000 rows of mrcntyfips variable in natl2003 dataset :

   Mother's |
  County of |
  Residence |
 (FIPS) U;R |      Freq.     Percent        Cum.
------------+-----------------------------------
          3 |          2        0.02        0.02
         20 |      4,265       42.65       42.67
         25 |          1        0.01       42.68
         27 |          1        0.01       42.69
         31 |          1        0.01       42.70
         55 |          1        0.01       42.71
         73 |          2        0.02       42.73
        101 |          4        0.04       42.77
        125 |          1        0.01       42.78
        999 |      5,722       57.22      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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