Equimarginal Rule and Playing the Field

Textbook Definition of Equimarginal Rule: The condition wherein the ratio of marginal benefits to marginal costs must be equal for all good consumed to maximize total utility. For example, if I consume goods x, y, and z, I will optimize consumption so that MBx/MCx = MBy/MCy = MBz/MCz.

She-conomic Definition: Suppose I am dating two guys, Xavier and Yuri, and the cost of an additional date with each guy is equal to the constant opportunity cost of my time (let's say that's equal to $10). Suppose I can allocate 6 hours/week to dating, and I am currently spending 3 hours on each guy. As it stands now, the marginal hour I spend with Xavier gives me $25 worth of marginal satisfaction, while the marginal hour I spend with Yuri gives me $40 worth of satisfaction. Am I efficiently organizing my time resources? No! Mathematically, MBx/MCx = 25/10 and MBy/MCy = 40/10. Since 40/10 > 25/10, I can get more satisfaction from the marginal minute spent with Yuri. As such, I should spend less time with Xavier and more time with Yuri (maybe 1 hour and 5 hours, instead of 3 hours and 3 hours).

Does this sounds like rational behavior to you? Or is this theory just eccentric/heartless ranting? Of course, I would never endorse using the equimarginal rule to justify truly heinous, hurtful behavior, as seen in John Tucker Must Die. That said, I think even the kindest, most sensitive parent would counsel their son/daughter to focus on spending time with the individuals who make us most happy, and vice versa.

Optimization Rule and Knowing When it's Over

Textbook Definition of Optimization Rule: From the consumer's perspective, to maximize total benefit/(total utility), consume until marginal benefit equals marginal cost. From the producer's perspective, produce until marginal revenue equals marginal cost.

She-conomic Definition: Keep dating someone until the marginal benefit (the extra happiness or satisfaction you feel for each additional date with "Bill") is equal to the marginal cost (the additional costs of time/money/anxiety you feel on each additional date.) Ignore sunk costs (e.g., all that money you "sunk" into taking him out to Chef's Table, the emotional trauma of meeting his parents, all those pictures on Facebook of you and he at Temple Square. . . .)

Opportunity Costs, THERE IS NO SUCH THING AS A FREE DATE (Even for Girls)

Textbook Definition of Opportunity Cost: the value of the best foregone option.

She-conomic Definition: the experience of going out with the second-best guy/girl you could have gone out is the "cost" of a date with a given person.

Many years ago I was asked to a dance, and I later found out that I was my date's second choice (he asked another girl first, but she already had a date). Had he been able to go out with Girl #1, the wonderful, intellectually exciting experience he would have had by spending the evening with the Sassy She-conomist would have been the opportunity cost of going out with Girl #1. Make sense?

LOL.

Sunk Costs and Unhappy Relationships

Textbook Definition of Sunk Costs: Fixed costs that cannot be recovered once they have occurred.

She-conomic Definition: All the past time/money/tears you "invested" in a relationship. Since these costs occurred in the past, they are "sunk."

Have you ever had a friend/roommate/acquaintance who prolonged an unhappy relationship for months and years just because she felt like she had "invested so much" in the relationship and didn't want to walk away after all of that effort? Better to cut your losses, I say. (I wonder if Pam Beesly would have dumped Roy sooner if she had had a better understanding of sunk costs. No need to prolong a sub-optimal relationship just because he was your high school sweetheart.)

Marginal Cost (a Brief Primer)

Textbook Definition: The additional cost of consuming one additional unit; also, the additional cost of producing one additional unit.

She-conomic Definition: The extra cost of going out with a guy one more time.

Marginal Benefit

Textbook Definition: The additional benefit gained by increasing consumption by one unit. Marginal benefit can be used in other contexts, too. For example, a the marginal benefit to a firm is called "marginal revenue"--the extra revenue gained by increasing production by one unit.

She-conomic Definition: The extra "happiness" or "satisfaction" obtained by going out with a guy one more time.