Frequencies for first 10,000 rows of vyear variable in namcs2006 dataset :

    year of |
      visit |      Freq.     Percent        Cum.
------------+-----------------------------------
       2005 |         56        0.56        0.56
       2006 |      9,944       99.44      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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