Frequencies for msr_strt_qtr variable in vwmeasure_dates dataset :

msr_strt_qt |
          r |      Freq.     Percent        Cum.
------------+-----------------------------------
     1Q2011 |          9       11.69       11.69
     1Q2012 |         14       18.18       29.87
     3Q2009 |         22       28.57       58.44
     3Q2011 |          1        1.30       59.74
     4Q2010 |          1        1.30       61.04
     4Q2011 |         30       38.96      100.00
------------+-----------------------------------
      Total |         77      100.00

by Jean Roth , jroth@nber.org , 16 Nov 2016