Frequencies for first 10,000 rows of cig_1 variable in linkpe2009psden dataset :

 Cigarettes |
        1st |
Trimester R |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      6,576       65.76       65.76
         90 |          1        0.01       65.77
         99 |          1        0.01       65.78
          . |      3,422       34.22      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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