Frequencies for statefips variable in countymd1989 dataset :

  The State |
    Federal |
Information |
 Processing |
     System |
(FIPS) code |      Freq.     Percent        Cum.
------------+-----------------------------------
         24 |         25      100.00      100.00
------------+-----------------------------------
      Total |         25      100.00

by Jean Roth , jroth@nber.org , 23 Jun 2017