Frequencies for first 10,000 rows of hmo variable in nhamcsopd1999 dataset :

       does |
    patient |
  belong to |
    an hmo? |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      2,720       27.20       27.20
          2 |      5,015       50.15       77.35
          3 |      2,099       20.99       98.34
          4 |        166        1.66      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 28 Mar 2016