Difference between revisions of "Economic definition of true love"

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This page was originally posted in September 2011 with humorous intent. To my surprise it has now received almost 500 distinct hits, and over 700 views. In the hope of appeasing my future audience, and just possibly getting a date out of it, I will now start adding actual content here. Though, most of it won't help you if you are actually interested in dating me. If that's the case, the best course of action is to email or call.
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==Preamble==
  
==Current Availability==
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I originally tried to write an [[economic definition of true love]] for Valentine's Day in 2009 on a page entitled "Dating Ed". It became one of the most popular pages on my website, receiving hundreds of thousands of views, and I maintained it across several different wikis. The version below no longer includes information about dating me, as I'm now married, but does bring back some other material that was deleted over the years. 
  
Ed is '''tentatively available''' for dating again.
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==Definition of True Love==
 
 
If you genuinely believe:
 
 
 
:<math>p\left(You \cap The\,One \ne \{\empty\}\,|\,First\,Glance\right) \gg 0</math>
 
 
 
then please stalk me at your earliest convenience.
 
 
 
It should be entirely unnecessary for me to suggest that you have at least one graduate degree with a basis in a mathematical discipline (i.e. math(s), econ, physics, engineering, etc.), as I would assume that you've stopped reading by now if you don't.
 
 
 
==Rules of Dating==
 
 
 
===The Age Rule===
 
 
 
I was unable to find a reference for the defacto standard age rule, but I believe it is a follows:
 
 
 
Let <math>Age_i \le Age_j</math>, then<math>Age_i \ge \left(\frac{Age_j}{2}\right)+7</math>
 
 
 
 
 
==True Love==
 
 
 
===Definition===
 
  
 
Let <math>H</math> denote the set of all entities (perhaps Humans, though we might also include dogs, cats and horses, according to historical precedent).
 
Let <math>H</math> denote the set of all entities (perhaps Humans, though we might also include dogs, cats and horses, according to historical precedent).
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Let <math>T</math> denote the set of pairs of individuals who have True Love, such that:
 
Let <math>T</math> denote the set of pairs of individuals who have True Love, such that:
  
:<math>\forall\{i,j\} \in T: \quad (i \succ_j h \quad \forall h \ne i) \and (j \succ_i h \quad \forall h \ne j), \quad h \in H \cap \{\emptyset\}</math>
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:<math>\forall\{i,j\} \in T: \quad (i \succ_j h \quad \forall h \ne i) \wedge (j \succ_i h \quad \forall h \ne j), \quad h \in H \cup \{\emptyset\}</math>
  
 
Note that:
 
Note that:
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*The union with the empty set allows for people who would rather be alone (e.g. Liz Lemon/Tina Fey), provided that we allow a mild abuse of notation so that <math>\{\emptyset\} \succ_{i} h</math>.
 
*The union with the empty set allows for people who would rather be alone (e.g. Liz Lemon/Tina Fey), provided that we allow a mild abuse of notation so that <math>\{\emptyset\} \succ_{i} h</math>.
  
===The Existence of True Love===
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==The Existence of True Love==
  
 
Can we prove that <math> T \ne \{\emptyset\}</math> ?
 
Can we prove that <math> T \ne \{\emptyset\}</math> ?
  
====The Brad Pitt Problem====
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===The Brad Pitt Problem===
  
 
Rational preferences aren't sufficient to guarantee that <math> T \ne \{\emptyset\}</math>.
 
Rational preferences aren't sufficient to guarantee that <math> T \ne \{\emptyset\}</math>.
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Recall that a preference relation is rational if it is complete and transitive:
 
Recall that a preference relation is rational if it is complete and transitive:
#Completeness: <math>\forall x,y \in X: \quad x \succsim y \;\or\; y \succsim x</math>
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#Completeness: <math>\forall x,y \in X: \quad x \succsim y \;\lor\; y \succsim x</math>
#Transitivity: <math>\forall x,y,z \in X: \quad \mbox{if}\; \; x \succsim y \;\and\; y \succsim x \;\mbox{then}\; x \succsim z</math>
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#Transitivity: <math>\forall x,y,z \in X: \quad \mbox{if}\; \; x \succsim y \;\wedge\; y \succsim z \;\mbox{then}\; x \succsim z</math>
  
 
Also recall the definition of the strict preference relation:
 
Also recall the definition of the strict preference relation:
:<math>x \succ y \quad \Leftrightarrow \quad x \succsim y \;\and\; y \not{\succsim} x</math>
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:<math>x \succ y \quad \Leftrightarrow \quad x \succsim y \;\wedge\; y \not{\succsim} x</math>
  
 
Then suppose:
 
Then suppose:
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Then <math>T = \{\emptyset\}</math>  Q.E.D.
 
Then <math>T = \{\emptyset\}</math>  Q.E.D.
  
====The Pitt-Depp Addendum====
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===The Pitt-Depp Addendum===
  
 
Adding the constraint that 'everybody loves somebody', or equivalently that:
 
Adding the constraint that 'everybody loves somebody', or equivalently that:
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Then <math>T = \{\emptyset\}</math>  Q.E.D.
 
Then <math>T = \{\emptyset\}</math>  Q.E.D.
  
Note: Objections to this proof on the grounds of the inclusion of Johnny Depp should be addressed to [http://elsa.berkeley.edu/~rabin/ Matthew Rabin].
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Note: Objections to this proof on the grounds of the inclusion of Johnny Depp should be addressed to [https://scholar.harvard.edu/rabin/capital-montana Matthew Rabin].
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==The Age Rule==
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The defacto standard age rule is as follows:
 +
 
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Denote two people <math>i\;</math> and <math>j\;</math> such that <math>Age_i \le Age_j</math>, then it is acceptable for them to date if and only if
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:<math>Age_i \ge \max \left\{\left(\frac{Age_j}{2}\right)+7\;,\;\underline{Age}\right\}</math>
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where <math>\underline{Age} = 18 \;\mbox{if}\; Age_j \ge 18</math>, except in Utah.
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I finally found a source to attribute this to: XKCD predates my posting significantly with its [http://xkcd.com/314/ 'Standard Creepiness Rule'].
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==Random Love==
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An amusing exploration of Random Love was recently posted as [http://what-if.xkcd.com/9/ XKCD Blog article No. 9].

Latest revision as of 20:00, 18 December 2020

Preamble

I originally tried to write an economic definition of true love for Valentine's Day in 2009 on a page entitled "Dating Ed". It became one of the most popular pages on my website, receiving hundreds of thousands of views, and I maintained it across several different wikis. The version below no longer includes information about dating me, as I'm now married, but does bring back some other material that was deleted over the years.

Definition of True Love

Let [math]H[/math] denote the set of all entities (perhaps Humans, though we might also include dogs, cats and horses, according to historical precedent).

Let [math]T[/math] denote the set of pairs of individuals who have True Love, such that:

[math]\forall\{i,j\} \in T: \quad (i \succ_j h \quad \forall h \ne i) \wedge (j \succ_i h \quad \forall h \ne j), \quad h \in H \cup \{\emptyset\}[/math]

Note that:

  • The definition employs strict preferences. A polyamorous definition might allow weak preferences instead.
  • The union with the empty set allows for people who would rather be alone (e.g. Liz Lemon/Tina Fey), provided that we allow a mild abuse of notation so that [math]\{\emptyset\} \succ_{i} h[/math].

The Existence of True Love

Can we prove that [math] T \ne \{\emptyset\}[/math] ?

The Brad Pitt Problem

Rational preferences aren't sufficient to guarantee that [math] T \ne \{\emptyset\}[/math].

Proof:

Recall that a preference relation is rational if it is complete and transitive:

  1. Completeness: [math]\forall x,y \in X: \quad x \succsim y \;\lor\; y \succsim x[/math]
  2. Transitivity: [math]\forall x,y,z \in X: \quad \mbox{if}\; \; x \succsim y \;\wedge\; y \succsim z \;\mbox{then}\; x \succsim z[/math]

Also recall the definition of the strict preference relation:

[math]x \succ y \quad \Leftrightarrow \quad x \succsim y \;\wedge\; y \not{\succsim} x[/math]

Then suppose:

  1. [math]\forall j \ne i \in H \quad i \succ_j h \quad \forall h\ne i \in H\quad\mbox{(Everyone loves Brad)}[/math]
  2. [math]\{\emptyset\} \succ_i h \quad \forall h \in H\quad\mbox{(Brad would rather be alone)}[/math]

Then [math]T = \{\emptyset\}[/math] Q.E.D.

The Pitt-Depp Addendum

Adding the constraint that 'everybody loves somebody', or equivalently that:

[math]\forall i \in H \quad \exists h \in H \;\mbox{s.t. }\; h \succ_i \{\emptyset\}[/math]

does not make rational preferences sufficient to guarantee that [math] T \ne \{\emptyset\}[/math].

Proof:

Suppose:

  1. [math]\forall k \ne i,j \in H \quad i \succ_j h \quad \forall h\ne i,k \in H\quad\mbox{(Everyone, except Johnny, loves Brad)}[/math]
  2. [math]j \succ_i h \quad \forall h\ne j \in H\quad\mbox{(Brad loves Johnny)}[/math]
  3. [math]\exists h' \ne i,j \; \mbox{s.t.}\; h'\succ_j h \quad \forall h\ne h',i \in H\quad\mbox{(Johnny loves his wife)}[/math]

Then [math]T = \{\emptyset\}[/math] Q.E.D.

Note: Objections to this proof on the grounds of the inclusion of Johnny Depp should be addressed to Matthew Rabin.

The Age Rule

The defacto standard age rule is as follows:

Denote two people [math]i\;[/math] and [math]j\;[/math] such that [math]Age_i \le Age_j[/math], then it is acceptable for them to date if and only if

[math]Age_i \ge \max \left\{\left(\frac{Age_j}{2}\right)+7\;,\;\underline{Age}\right\}[/math]

where [math]\underline{Age} = 18 \;\mbox{if}\; Age_j \ge 18[/math], except in Utah.

I finally found a source to attribute this to: XKCD predates my posting significantly with its 'Standard Creepiness Rule'.

Random Love

An amusing exploration of Random Love was recently posted as XKCD Blog article No. 9.