Frequencies for first 10,000 rows of vyear variable in namcs1999 dataset :

    year of |
      visit |      Freq.     Percent        Cum.
------------+-----------------------------------
       1998 |        212        2.12        2.12
       1999 |      9,788       97.88      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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