Frequencies for first 10,000 rows of ld_chor variable in natlterr2014 dataset :

Chorioamnio |
nitis Y Yes |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      1,077       10.77       10.77
          N |      8,750       87.50       98.27
          U |        157        1.57       99.84
          Y |         16        0.16      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 15 Jun 2016