Frequencies for first 10,000 rows of yearref variable in countypopmonthasrh dataset :

                                  Year |      Freq.     Percent        Cum.
---------------------------------------+-----------------------------------
        1 = 4/1/2010 Census population |      3,334       33.34       33.34
2 = 4/1/2010 population estimates base |      3,333       33.33       66.67
3 = 7/1/2010 population estimates base |      3,333       33.33      100.00
---------------------------------------+-----------------------------------
                                 Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 12 May 2018