Frequencies for first 10,000 rows of popvism variable in nhamcsopd1996 dataset :

  estimated |
   provider |
      visit |
     volume |
   (masked) |      Freq.     Percent        Cum.
------------+-----------------------------------
         -1 |     10,000      100.00      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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