Frequencies for type variable in form2010 dataset :

    Type of |
     format |      Freq.     Percent        Cum.
------------+-----------------------------------
          C |          9        0.26        0.26
          N |      3,401       99.74      100.00
------------+-----------------------------------
      Total |      3,410      100.00

by Jean Roth , jroth@nber.org , 18 Apr 2016