Frequencies for ptype variable in impact2004 dataset :

   Provider |
       Type |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      3,041       73.51       73.51
          7 |        187        4.52       78.03
          8 |         42        1.02       79.04
         14 |        257        6.21       85.26
         16 |        523       12.64       97.90
         17 |         81        1.96       99.85
         21 |          4        0.10       99.95
         22 |          2        0.05      100.00
------------+-----------------------------------
      Total |      4,137      100.00

by Jean Roth , jroth@nber.org , 17 Mar 2016