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    Mothers attempting to balance parenthood and academics.


Math Geek Mom: “That Sunk Theory”

Disney and economics.


April 7, 2016

Years ago, a former student told me that he suspected that I found examples of Economics everywhere I looked, which is basically true. I thought of this comment a few weeks ago when one of the top economists in my sub-field sent me a reference to the classic paper “A Disneyland Dilemma: Two-Part Tariffs for a Mickey Mouse Monopoly” when he heard that I would be going to Disneyworld for my daughter’s spring break.

The article, from the Quarterly journal of Economics in 1971 (the year Disneyworld in Florida was built) talks about the optimal fee to charge patrons who come to a park and want to ride the rides. Relating it to economic theory, it proposes what that the optimal fee should be. This vaguely relates to something I had already noticed; Disneyworld sells “fastpasses” to its patrons to essentially cut in line for desirable rides that otherwise often can have waiting times of over two hours.

This reminded me of something a former colleague from a Philosophy department sometimes calls “that sunk theory.” He is referring to the idea of “sunk cost,” that decisions should be made looking into the future, and not in reference to what was invested to get to that point. The money and time spent to get to a point where a decision is made, it proposes, are already spent; they are “sunk costs,” and should not enter into your further decisions. If you pay to get into a movie and then realize that you are not enjoying it, should you stay and watch it? The fee to get into the movie is a “sunk cost,” and you should only consider your enjoyment from that point on.

 I found myself thinking of this after I rode a ride for which our vacation planner had given us a fastpass. With the words “seven dwarfs” in its name, I thought it would be similar to many of the other rides in the park, with animated figures that sang and danced. However, only seconds onto the ride, it became clear that this was a roller coaster. As someone with motion sickness who does not enjoy roller coasters, I endured the next few minutes, getting a candid photo of myself taken along the way. When my husband and daughter found the picture, they had a good laugh. Were they going to buy it? Of course they were. What was the price? They both told me that it was priceless.

That taught me to ask whether each ride was a roller coaster before getting on it. One woman in front of me going into the Haunted Mansion might have had a similar experience, since she nodded when I asked, telling me that it was always good to ask. My daughter, of course, was mortified. I decided that the fact that our vacation planner had booked us for many fastpasses on roller coasters was simply a “sunk cost.” I had them, but could choose not to use them. Which is what I did.

I had been to Disneyworld once before, almost forty years ago, when it was much smaller and still very new. My last memory of that first visit was of riding away on the monorail with my family, Cinderella’s castle fading off in the distance. One of my last memories of this visit was of dinner with my own family at a restaurant overlooking that castle and a woman on a ukulele singing “Somewhere Over the Rainbow,” bringing me to tears as I thought of all that had happened in the time between those two views of the castle. I recalled forty years of days, some ecstatically happy and days that were inconsolably sad. My daughter suggested that maybe we would all come back with her children, someday.

That week, my husband found himself riding a few more roller coasters than his fifty-something body enjoyed, and my daughter had a fabulous time. She has caught the vacationing bug, and suggested a place for a vacation next year. However, with all due respect to the island paradise she showed us on her phone, I doubt very much that we will soon be taking a trip to Bora Bora.


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