Frequencies for calculationperiod variable in hvbp_quarters dataset :

          Calculation Period |      Freq.     Percent        Cum.
-----------------------------+-----------------------------------
April 1, 2012 - Dec 31, 2012 |         14       82.35       82.35
July 1, 2011 - June 30, 2012 |          3       17.65      100.00
-----------------------------+-----------------------------------
                       Total |         17      100.00

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