Frequencies for first 10,000 rows of psum variable in nhamcsed1993 dataset :

 psu marker |
   (masked) |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      4,568       45.68       45.68
          2 |      3,430       34.30       79.98
          3 |      1,808       18.08       98.06
          4 |        194        1.94      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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