As usual you take the data and use them as you please. In fact if you look at the dollar figure you can see that the situation is quite different : 17M$ for Frozen vs $ 11M$ for DM2. This is because the DVD of DM2 was sold at hard discounted price during the release of the movie Minions. The same happened in the Blu-Ray chart.
Average price in 2015 in USA
Frozen
DVD 19,90$
BD 24,90$
DM2
DVD 11,50$
BD 13,90$
Total units sold/gross in lifetime in USA
Frozen BD 7,26M (top seller ever in USA) + DVD 11,95 = 19,21M (356,7M$)
DM2 BD 5,81M + DVD 8,02 = 13,83M (237,4M$)