Frequencies for ndc variable in nadacc20160406 dataset :

   National |
  Drug Code |
      (NDC) |      Freq.     Percent        Cum.
------------+-----------------------------------
50419040303 |          1        7.14        7.14
50419040703 |          1        7.14       14.29
50419040903 |          1        7.14       21.43
52544023631 |          1        7.14       28.57
59630058030 |          1        7.14       35.71
59630058090 |          1        7.14       42.86
64896066101 |          1        7.14       50.00
64896066143 |          1        7.14       57.14
64896066201 |          1        7.14       64.29
64896066243 |          1        7.14       71.43
64896066301 |          1        7.14       78.57
64896066343 |          1        7.14       85.71
64896066401 |          1        7.14       92.86
64896066443 |          1        7.14      100.00
------------+-----------------------------------
      Total |         14      100.00

by Jean Roth , jroth@nber.org , 10 Feb 2018