Frequencies for first 10,000 rows of vyear variable in nhamcsopd2000 dataset :

    year of |
      visit |      Freq.     Percent        Cum.
------------+-----------------------------------
       1999 |        154        1.54        1.54
       2000 |      9,846       98.46      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 28 Mar 2016