Frequencies for first 10,000 rows of year variable in zipcode2011 dataset :

       Year |      Freq.     Percent        Cum.
------------+-----------------------------------
       2011 |     10,000      100.00      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 26 Jun 2017