Frequencies for first 10,000 rows of psum variable in nhamcsopd1995 dataset :

 psu marker |
   (masked) |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      5,542       55.42       55.42
          2 |      3,709       37.09       92.51
          3 |        584        5.84       98.35
          4 |        165        1.65      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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