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

   hospital |
   sampling |
unit marker |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      8,233       82.33       82.33
          2 |        934        9.34       91.67
          3 |        467        4.67       96.34
          4 |        318        3.18       99.52
          5 |         48        0.48      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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