Frequencies for first 10,000 rows of urf_phyper variable in natlterr2005 dataset :

  Pregnancy |
 Associated |
Hypertensio |
      n U;R |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        205        2.05        2.05
          2 |      8,008       80.08       82.13
          9 |      1,787       17.87      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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