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Today i want to talk to you

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about the mathematics of love.

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I think we can all agree [br]that mathematicians

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are famously excellent [br]at finding love.

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But it's not just because[br]of our dashing personalities

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our superior conversational skills

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or our excellent pencil cases,

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it's also because we've done

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a lot of work into the maths

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of how to find the perfect partner.

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in my favorite paper on the subject

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which is entitled, [br]

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"Why I Don't Have a Girlfriend."

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peter backus tries to rate

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his chances at finding love

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now, peter is not a very greedy man

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of all of the available women in the UK

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all that peter's looking for is

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somebody who lives near him,

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somebody in the right age range,

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somebody with a university degree,

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somebody he's likely to get on well with

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somebody attractive

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somebody who is likely to find him attractive

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(laughter)

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and comes up with an estimate of 26 women

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in the whole of the UK

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it's not looking very good, is it peter?

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now just to put that into perspective

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that's about 400 times fewer

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than the best estimates

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of how many intelligent[br]extra-terrestrial life forms there are

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and it also gives peter a

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1 in 285,000 of bumping[br]into any one of these special ladies

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on a night out

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I'd like to think that's why

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mathematicians don't really bother

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going on nights out anymore

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The thing is is that i personally

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don't subscribe to such a pessimistic view

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i know, just as well as you do,

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that love doesn't really work like that

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human emotion isn't neatly ordered

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rational or easily predictable

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but i also know that that doesn't mean[br]that mathematics

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doesn't have something it can offer us

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because, love, as with most of life

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is full of patterns

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and mathematics is ultimately

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all about the study of patterns

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pattersn from predicting the weather

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to the fluctuations of the stock market

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to the movement of the planets

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or the growth of cities

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if we're being honest, none

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of those things are neatly ordered

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or easily predictable either

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because i believe that mathematics

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is so powerful that is has the potential

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to offer us a new way of looking

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at almost anything

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even something as mysterious as love

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and so, to try to persuade you

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of how totally, excellent, [br]and relevant mathematics is

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I want to give you my top three

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mathematically verifiable tips for love

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okay, so, top tip #1

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how to win at online dating

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so my favorite online dating website

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is OkayCupid

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not least because it was

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started by a group of mathematicians

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now because they're mathematicians

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they have been collecting

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data on everyone whose been using

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their site for almost a decade

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and they've been trying to search

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for patterns in the way that we

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talk about ourselves

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and the way that we interact with each other

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on online dating websites

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and they've come up with

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seriously interesting findings

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but my particular favorite

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is that it turns out

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that one an online dating website,

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how attractive you are

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does not dictate how popular you are

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and actually having people

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think that you're ugly can

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work to your advantage

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let me show you how this works

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okay, in a thankfully voluntary section

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you are allowed to rate how attractive people are

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between 1 and 5

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and if we compare this score

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this average score

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to how many messages a selection

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of people receive

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you can begin to get a sense

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of how attractiveness

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links to popularity on online dating

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so this is a graph that the online

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okay cupid guys have come up with

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and the important thing

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to notice is that it's not totally true

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that the more attractive you are

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the more messages you get

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but the question arises then

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of what is it about people up here

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who are so much more popular

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than people down here?

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even though they have the

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same score of attractiveness

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and the reason why is that

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it's not just straight forward looks

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that are important

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so, let me try to illustrate their findings

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with an example

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if you take someone like porcia di rossi

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everybody agrees that porcia di rossi

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is a very beautiful woman

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nobody thinks that she's ugly

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but she's not a supermodel

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if you compare porcia di rossi

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to someone like sarah jessica parker

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now, a lot of people

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myself included

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think that sarah jessica parker

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is seriously fabulous

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and possibly one of

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the most beautiful creatures to have evr

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walked the face of the earth

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but, some other people

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e.i., most of the internet

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seem to think that she looks a bit like a horse

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(laughter)

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now, i think that if you ask people

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how attractive sarah jessica parker [br]or porcia di rossi are

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and you ask them to give them a score between one and five

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i reckon that they would average out to the same score

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but the way that people would vote

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would be dry different

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so porcia's scores would all be clustered around

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the four because everybody agrees that she's

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very beautiful

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whereas sarah jessica parker divides opinion

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there a huge spread in her scores

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and actually it's this spread that counts

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it's this spread that makes you more popular

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on online internet dating websites

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so what this means then

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is that if some people think that [br]you're attractive

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you're actually better off[br]having some other people

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think that you're a massive minger

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that's much better than everybody[br]thinking that you're the cute girl next door

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i think that this makes a bit more sense

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when you think in terms of the people

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who are sending these messages

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so let's say that you think somebody's attractive

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but you suspect that other people

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won't necessarily be that interested

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that means that there is less competition for you

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and that there's an extra incentive

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for you to get in touch

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whereas compare that to if you think

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somebody is attractive but

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you suspect that everybody is going

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to think they're attractive

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well, why would you bother humiliating yourself

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here's where the really interesting part comes

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people choose the pictures[br]that they use on an online, dating website

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they often try to minimize the things

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that they think people will find unattractive

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the classic example is that

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people who are a little but overweight

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deliberately choosing a very cropped phto

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or bald men for example

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deliberatly choosing pictures

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where they're wearing hats

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but this is the opposite of

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what you should do if

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want to be succesful

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you should really instead

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play up to whatever it is that makes you different

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even if you think that

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some people will find you unattractive

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because the people who fancy you

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are just going to fancy you anyway

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and the unimportant losers who don't

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well, they only play out to you r advantage

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Okay, top tip #2, how to pick[br]the perfect partner

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so let's imagine then that[br]you're a roaring success

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on the dating scene

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but the question arises of how[br]do you then convert

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that success into longer term happiness

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and in particular,

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how do you decide when is the

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right time to settle down

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now generally, it's not advisable

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to just cash in the first person

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who comes along and shows you any interest

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at all

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but, equally, you don't want to leave it

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too long if you want to maximize your [br]chances of long term happiness

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as my favorite author, jane austen put it,

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"an unmarried woman of seven and twenty

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can never hope to feel or

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inspire affection again."

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laughter

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thanks, jane

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so the question is then

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how do you know when is the right

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time to settle down

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given all the people that you

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can date in your lifetime

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thankfully, there is a rather delicious bit

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of mathematics that we can use to

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help us out here

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so lets imagine then,

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that you start dating when you're 15

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and ideally, you'd like to be

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married by the time you're 35

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the number of people that you

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could potentially date across your lifetime

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and they'll be at kind of varying levels

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of goodness

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now the rules are that when you cash in

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and get married

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you can't look ahead and see

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what you could have had

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and equally, you can't go back

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and change your mind

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in my experience at least

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i find that people don't typically

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like being recalled years after

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being passed up

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for somebody else, or that's just me

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so the math says then

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that what you should do

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in the first 37 percent of your dating window

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you should reject everybody [br]as serious marriage potential

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and then, you should pick the [br]next person who comes along

9:59:59.000,9:59:59.000
who is better than everyone that you've seen before

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so here's the example

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now if you do