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

Hydramnios/ |
Oligohydram |
   nios RFP |
686=f_urf_h |
     ydra U |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        144        1.44        1.44
          2 |      9,712       97.12       98.56
          9 |        144        1.44      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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