Frequencies for first 10,000 rows of vmonth variable in nhamcsopd1995 dataset :

   month of |
      visit |      Freq.     Percent        Cum.
------------+-----------------------------------
    January |      1,302       13.02       13.02
   February |        803        8.03       21.05
      March |        734        7.34       28.39
      April |        747        7.47       35.86
        May |        847        8.47       44.33
       June |      1,112       11.12       55.45
       July |        979        9.79       65.24
     August |        724        7.24       72.48
  September |        495        4.95       77.43
    October |        658        6.58       84.01
   November |        688        6.88       90.89
   December |        911        9.11      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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