Rational Grocery Shopping

Our discussion about how Economics has changed the way we think reminded me of a blog post drafted deep in my notes, so here it is. I have to admit that Econ has truly affected my decision making, even at the grocery store.

When I visit the grocery store, I pretty much buy the same things every time, resulting in a total around $80. I usually buy Amy’s Veggie Burgers, which come in packs of four for $5.99. If I’m feeling frivolous, I will buy Beyond Burger Plant Based Patties, which taste better and come in packs of two for $5.49. During my recent shopping trip, I remember walking up to the Beyond Burgers, contemplating picking them up, but then looking at the price. In that moment, I had remembered that I had an entire package of Amy’s burgers at home. So, I turned around and did not purchase the Beyond Burgers. 

What I didn’t realize until after the shopping trip was that I had subconsciously evaluated my marginal benefit versus marginal costs. The marginal cost of one Beyond Burger is $2.75, while the marginal cost of one Amy’s burger is $1.50. Plus, I knew I had previously purchased Amy’s burgers, a sunk cost of $5.99, and hadn’t even opened the package yet. My marginal benefit would've decreased if I had increased my possession from four to six veggie burgers, since I would've felt irrational about spending more money on veggie burgers when I already had four patiently waiting to be eaten. Personally, the marginal benefit for one Beyond Burger is not equal to the marginal cost of one ($2.75), and I can only eat so many veggie burgers before the marginal utility rapidly drops. If more people took Economics classes maybe they would be rational grocery shoppers like myself. 

(Note: On subsequent shopping trips I did not act rationally and bought the Beyond Burgers anyway, despite already having veggie burgers at home).