Frequencies for first 10,000 rows of popsum variable in nhamcsopd2000 dataset :

     no. of |
     clinic |
   sampling |
   units in |
   hospital |
   (masked) |      Freq.     Percent        Cum.
------------+-----------------------------------
         -1 |      6,217       62.17       62.17
          0 |      3,783       37.83      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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