Variable Costing and the Effect of Sales and Production
on Operating Income
Given a constant contribution margin per unit and constant fixed costs, the period-toperiod
change in operating income under variable costing is driven solely by changes in
the quantity of units actually sold. Consider the variable-costing operating income of
Stassen in (a) 2013 versus 2012 and (b) 2014 versus 2013. Recall the following: