Frequencies for first 10,000 rows of poppsum variable in namcs1993 dataset :

    stratum |
  counts of |
       psus |
   (masked) |      Freq.     Percent        Cum.
------------+-----------------------------------
         -1 |      5,443       54.43       54.43
          1 |      4,557       45.57      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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