Frequencies for first 10,000 rows of f_api variable in natl2009 dataset :

  API Codes |
(unrevised) |
          U |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |         38        0.38        0.38
          . |      9,962       99.62      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 22 Dec 2015