Frequencies for ptype variable in impact2011 dataset :

   Provider |
       Type |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      2,679       75.44       75.44
          7 |        180        5.07       80.51
          8 |         33        0.93       81.44
         14 |        194        5.46       86.91
         15 |         13        0.37       87.27
         16 |        332        9.35       96.62
         17 |        117        3.29       99.92
         21 |          3        0.08      100.00
------------+-----------------------------------
      Total |      3,551      100.00

by Jean Roth , jroth@nber.org , 16 Dec 2016