Pay more for the same thing or pay the same for less of a thing?

At the supermarket yesterday, I noticed my brand of shampoo went from 15 ounces to 12.5 ounces. The bottle was still the same height but narrower. This goes back to the great orange juice conspiracy of 2009 when half a gallon went from 64 to 59 fluid ounces. Same price, just less.

What do you think?