Frequencies for first 10,000 rows of left variable in nhamcsed2001 dataset :

left before |
 being seen |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,849       98.49       98.49
          1 |        151        1.51      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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