Frequencies for first 10,000 rows of vyear variable in nhamcsed2000 dataset :

    year of |
      visit |      Freq.     Percent        Cum.
------------+-----------------------------------
       1999 |        146        1.46        1.46
       2000 |      9,854       98.54      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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