Frequencies for first 10,000 rows of prov3810 variable in posclia2009 dataset :

  cert type |
   code # 1 |      Freq.     Percent        Cum.
------------+-----------------------------------
            |        290        2.90        2.90
          1 |      1,120       11.20       14.10
          2 |      5,397       53.97       68.07
          3 |        803        8.03       76.10
          4 |      2,053       20.53       96.63
          9 |        337        3.37      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 26 Jan 2016