Frequencies for first 10,000 rows of mrcntyfips variable in linkpe2009psden dataset :

   Mother's |
FIPS County |
         of |
  Residence |
 (FIPS) U;R |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |          7        0.07        0.07
        127 |        666        6.66        6.73
        999 |      9,327       93.27      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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