Frequencies for first 10,000 rows of srefmon variable in sipprw08w1 dataset :

SU: Reference month of |
           this record |      Freq.     Percent        Cum.
-----------------------+-----------------------------------
 First Reference month |      2,498       24.98       24.98
Second Reference month |      2,498       24.98       49.96
 Third Reference month |      2,500       25.00       74.96
Fourth Reference month |      2,504       25.04      100.00
-----------------------+-----------------------------------
                 Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 3 Jan 2016