Frequencies for first 10,000 rows of venl30 variable in linkco1991us_num dataset :

   Assisted |
ventilation |
- less than |
 30 minutes |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        262        2.62        2.62
          2 |      8,587       85.87       88.49
          8 |         10        0.10       88.59
          9 |      1,141       11.41      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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