Frequencies for first 10,000 rows of urf_phyper variable in natl2005 dataset :

  Pregnancy |
 Associated |
Hypertensio |
      n U;R |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        435        4.35        4.35
          2 |      9,442       94.42       98.77
          9 |        123        1.23      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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