Movie theaters already make the list of places that rip you off, but they could enter a whole new swindling category. According to UC Irvine professor Richard McKenzie in his new Freakonomics-esque book Why Popcorn Costs So Much at the Movies, And Other Pricing Puzzles, there's a more than 50 percent chance that medium bag with flexible sides is a better bang for your buck than the large tub with constricting, rigged sides.
McKenzie points out that this excludes the free refills caveat included with the large portion. He argues that at least half of people don't take advantage of this bottomless popcorn perk, and if you do, you're safe. The popcorn-scooping clerk is also a factor here, since he or she can stuff the medium bag to maximum occupancy by pressing down with force. Moral of the story to McKenzie's research? Order the medium, and wink like crazy at the high schooler on scoop duty.