Frequencies for first 10,000 rows of f_clinest variable in natl2006 dataset :

   Clinical |
Estimate of |
  Gestation |
  (estgest) |
        U;R |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |          6        0.06        0.06
          1 |      9,994       99.94      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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