Frequencies for first 10,000 rows of left variable in nhamcsed1999 dataset :

left before |
 being seen |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,829       98.29       98.29
          1 |        171        1.71      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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