Frequencies for first 10,000 rows of stratm variable in nhamcsed2002 dataset :

psu stratum |
     marker |
   (masked) |      Freq.     Percent        Cum.
------------+-----------------------------------
        201 |      6,032       60.32       60.32
        202 |      2,932       29.32       89.64
        203 |        820        8.20       97.84
        204 |        216        2.16      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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