Frequencies for first 10,000 rows of vyear variable in namcs2007 dataset :

    year of |
      visit |      Freq.     Percent        Cum.
------------+-----------------------------------
       2006 |        224        2.24        2.24
       2007 |      9,776       97.76      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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