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	<title>Comments on: Mathematically correct but psychologically wrong</title>
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	<link>http://www.johndcook.com/blog/2010/11/02/snowball-strategy/</link>
	<description>John D. Cook</description>
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		<title>By: CandlestickPicks.com &#8211; Mathematically Optimal but Psychologically Wrong</title>
		<link>http://www.johndcook.com/blog/2010/11/02/snowball-strategy/comment-page-1/#comment-18147</link>
		<dc:creator>CandlestickPicks.com &#8211; Mathematically Optimal but Psychologically Wrong</dc:creator>
		<pubDate>Sun, 09 Sep 2012 01:14:33 +0000</pubDate>
		<guid isPermaLink="false">http://www.johndcook.com/blog/?p=6955#comment-18147</guid>
		<description><![CDATA[[...] a good article that relates quite a bit to trading. John Cook discusses debt consolidation and the debt-snowball strategy. His point is that the even though it&#8217;s mathematically optimal [...] ]]></description>
		<content:encoded><![CDATA[<p>[...] a good article that relates quite a bit to trading. John Cook discusses debt consolidation and the debt-snowball strategy. His point is that the even though it&#8217;s mathematically optimal [...] </p>
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		<title>By: Zb</title>
		<link>http://www.johndcook.com/blog/2010/11/02/snowball-strategy/comment-page-1/#comment-18146</link>
		<dc:creator>Zb</dc:creator>
		<pubDate>Sat, 12 Feb 2011 23:12:24 +0000</pubDate>
		<guid isPermaLink="false">http://www.johndcook.com/blog/?p=6955#comment-18146</guid>
		<description><![CDATA[Actually, the snowball strategy IS the mathematically optimal way to go if one takes into account a mathematical variable for the psychological factor to calculate an &quot;Effective Debt&quot;:

Monetary debt = M
Effective debt = M - P(n)

where P(n) = psychological inclination as a function of n number of accounts with a balance; note P(n)=0 only for androids or people w/ no emotions

In this case, P(n) increases with decreasing n. For a person with n=10 credit cards, say P(n) = -10,000

If M = $30,000 and P(10)= -10,000,
Effective debt = $40,000

...Getting rid of two accounts by paying them off (even if they owed say $1,000 on each account) has an additional psychological benefit in that now P(n) = P(8) = -8,000

causing
Effective debt (of 8 accounts) = $26,000  

But as a counterexample, if the same $2,000 was targeted toward accounts with the highest interest rate without actually resulting in any reduced # of accounts, P(n) would still be equal to P(10) = 10,000

and 

Effective debt  (of 10 accounts) = $28,000

That&#039;s how you incorporate psychology into mathematics and allow the math to do its thing!

Zb]]></description>
		<content:encoded><![CDATA[<p>Actually, the snowball strategy IS the mathematically optimal way to go if one takes into account a mathematical variable for the psychological factor to calculate an &#8220;Effective Debt&#8221;:</p>
<p>Monetary debt = M<br />
Effective debt = M &#8211; P(n)</p>
<p>where P(n) = psychological inclination as a function of n number of accounts with a balance; note P(n)=0 only for androids or people w/ no emotions</p>
<p>In this case, P(n) increases with decreasing n. For a person with n=10 credit cards, say P(n) = -10,000</p>
<p>If M = $30,000 and P(10)= -10,000,<br />
Effective debt = $40,000</p>
<p>&#8230;Getting rid of two accounts by paying them off (even if they owed say $1,000 on each account) has an additional psychological benefit in that now P(n) = P(8) = -8,000</p>
<p>causing<br />
Effective debt (of 8 accounts) = $26,000  </p>
<p>But as a counterexample, if the same $2,000 was targeted toward accounts with the highest interest rate without actually resulting in any reduced # of accounts, P(n) would still be equal to P(10) = 10,000</p>
<p>and </p>
<p>Effective debt  (of 10 accounts) = $28,000</p>
<p>That&#8217;s how you incorporate psychology into mathematics and allow the math to do its thing!</p>
<p>Zb</p>
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		<title>By: Vikan á netinu &#8211; Arnþór Snær</title>
		<link>http://www.johndcook.com/blog/2010/11/02/snowball-strategy/comment-page-1/#comment-18145</link>
		<dc:creator>Vikan á netinu &#8211; Arnþór Snær</dc:creator>
		<pubDate>Mon, 22 Nov 2010 17:17:04 +0000</pubDate>
		<guid isPermaLink="false">http://www.johndcook.com/blog/?p=6955#comment-18145</guid>
		<description><![CDATA[[...] Shared Mathematically correct but psychologically wrong. [...] ]]></description>
		<content:encoded><![CDATA[<p>[...] Shared Mathematically correct but psychologically wrong. [...] </p>
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		<title>By: Lucian</title>
		<link>http://www.johndcook.com/blog/2010/11/02/snowball-strategy/comment-page-1/#comment-18144</link>
		<dc:creator>Lucian</dc:creator>
		<pubDate>Sun, 07 Nov 2010 17:36:50 +0000</pubDate>
		<guid isPermaLink="false">http://www.johndcook.com/blog/?p=6955#comment-18144</guid>
		<description><![CDATA[this can be applied to business taxes, countries with a high number of taxes are doing very bad.]]></description>
		<content:encoded><![CDATA[<p>this can be applied to business taxes, countries with a high number of taxes are doing very bad.</p>
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		<title>By: John</title>
		<link>http://www.johndcook.com/blog/2010/11/02/snowball-strategy/comment-page-1/#comment-18143</link>
		<dc:creator>John</dc:creator>
		<pubDate>Wed, 03 Nov 2010 11:10:04 +0000</pubDate>
		<guid isPermaLink="false">http://www.johndcook.com/blog/?p=6955#comment-18143</guid>
		<description><![CDATA[Dan Ariely&#039;s publisher probably chose to use &quot;irrational&quot; in the title of his book to be provocative. In my opinion, &quot;irrational&quot; should be used to indicate an error in logic and not just taking into account factors that are difficult to model mathematically. 

If someone says &quot;I owe Sam $10 and I owe Jill $7. Therefore I&#039;m $5 in debt.&quot; they are being irrational. But if someone says &quot;My plan for eliminating my debt will take into account my understanding of human nature&quot; then I would say they are being rational.]]></description>
		<content:encoded><![CDATA[<p>Dan Ariely&#8217;s publisher probably chose to use &#8220;irrational&#8221; in the title of his book to be provocative. In my opinion, &#8220;irrational&#8221; should be used to indicate an error in logic and not just taking into account factors that are difficult to model mathematically. </p>
<p>If someone says &#8220;I owe Sam $10 and I owe Jill $7. Therefore I&#8217;m $5 in debt.&#8221; they are being irrational. But if someone says &#8220;My plan for eliminating my debt will take into account my understanding of human nature&#8221; then I would say they are being rational.</p>
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		<title>By: The Jaywalker</title>
		<link>http://www.johndcook.com/blog/2010/11/02/snowball-strategy/comment-page-1/#comment-18142</link>
		<dc:creator>The Jaywalker</dc:creator>
		<pubDate>Wed, 03 Nov 2010 07:09:32 +0000</pubDate>
		<guid isPermaLink="false">http://www.johndcook.com/blog/?p=6955#comment-18142</guid>
		<description><![CDATA[Mathematical strategy would have been equivalent to psychological strategy had we been rational, fully-logical beings. As Dan Ariel points out in two book, we are predictably irrational.]]></description>
		<content:encoded><![CDATA[<p>Mathematical strategy would have been equivalent to psychological strategy had we been rational, fully-logical beings. As Dan Ariel points out in two book, we are predictably irrational.</p>
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		<title>By: John Myles White</title>
		<link>http://www.johndcook.com/blog/2010/11/02/snowball-strategy/comment-page-1/#comment-18141</link>
		<dc:creator>John Myles White</dc:creator>
		<pubDate>Tue, 02 Nov 2010 16:04:52 +0000</pubDate>
		<guid isPermaLink="false">http://www.johndcook.com/blog/?p=6955#comment-18141</guid>
		<description><![CDATA[Great post. To me this is very similar to work by Loewenstein and Prelec (http://sds.hss.cmu.edu/media/pdfs/loewenstein/PreferencesSeqOutcomes.pdf) in the 90&#039;s showing that mathematical discounting models imply the exact opposite of people&#039;s true preferences for sequences of positive events.]]></description>
		<content:encoded><![CDATA[<p>Great post. To me this is very similar to work by Loewenstein and Prelec (<a href="http://sds.hss.cmu.edu/media/pdfs/loewenstein/PreferencesSeqOutcomes.pdf" rel="nofollow">http://sds.hss.cmu.edu/media/pdfs/loewenstein/PreferencesSeqOutcomes.pdf</a>) in the 90&#8242;s showing that mathematical discounting models imply the exact opposite of people&#8217;s true preferences for sequences of positive events.</p>
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		<title>By: John</title>
		<link>http://www.johndcook.com/blog/2010/11/02/snowball-strategy/comment-page-1/#comment-18140</link>
		<dc:creator>John</dc:creator>
		<pubDate>Tue, 02 Nov 2010 15:34:13 +0000</pubDate>
		<guid isPermaLink="false">http://www.johndcook.com/blog/?p=6955#comment-18140</guid>
		<description><![CDATA[Rob: I do something similar, particularly when I&#039;m feeling overwhelmed with my to do list. Knocking out a few little things makes me more willing to tackle the bigger ones.]]></description>
		<content:encoded><![CDATA[<p>Rob: I do something similar, particularly when I&#8217;m feeling overwhelmed with my to do list. Knocking out a few little things makes me more willing to tackle the bigger ones.</p>
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		<title>By: Mathematically Optimal but Psychologically Wrong &#124; StockTickr Trading Journal Blog</title>
		<link>http://www.johndcook.com/blog/2010/11/02/snowball-strategy/comment-page-1/#comment-18139</link>
		<dc:creator>Mathematically Optimal but Psychologically Wrong &#124; StockTickr Trading Journal Blog</dc:creator>
		<pubDate>Tue, 02 Nov 2010 15:30:09 +0000</pubDate>
		<guid isPermaLink="false">http://www.johndcook.com/blog/?p=6955#comment-18139</guid>
		<description><![CDATA[[...] a good article that relates quite a bit to trading. John Cook discusses debt consolidation and the debt-snowball strategy. His point is that the even though it&#8217;s mathematically optimal [...] ]]></description>
		<content:encoded><![CDATA[<p>[...] a good article that relates quite a bit to trading. John Cook discusses debt consolidation and the debt-snowball strategy. His point is that the even though it&#8217;s mathematically optimal [...] </p>
]]></content:encoded>
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		<title>By: Nirmal Patel</title>
		<link>http://www.johndcook.com/blog/2010/11/02/snowball-strategy/comment-page-1/#comment-18138</link>
		<dc:creator>Nirmal Patel</dc:creator>
		<pubDate>Tue, 02 Nov 2010 15:29:32 +0000</pubDate>
		<guid isPermaLink="false">http://www.johndcook.com/blog/?p=6955#comment-18138</guid>
		<description><![CDATA[@Ruben, @John: My pessimistic side was saying that debt consolidation companies probably do not work optimally in a mathematical sense. Instead they may compromise between mathematical optimality and getting the longest, most profitable payment system out of you before you decide that it&#039;s not worth it.]]></description>
		<content:encoded><![CDATA[<p>@Ruben, @John: My pessimistic side was saying that debt consolidation companies probably do not work optimally in a mathematical sense. Instead they may compromise between mathematical optimality and getting the longest, most profitable payment system out of you before you decide that it&#8217;s not worth it.</p>
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		<title>By: Ruben Berenguel</title>
		<link>http://www.johndcook.com/blog/2010/11/02/snowball-strategy/comment-page-1/#comment-18137</link>
		<dc:creator>Ruben Berenguel</dc:creator>
		<pubDate>Tue, 02 Nov 2010 15:12:14 +0000</pubDate>
		<guid isPermaLink="false">http://www.johndcook.com/blog/?p=6955#comment-18137</guid>
		<description><![CDATA[I wasn&#039;t aware from that quote from Stroustrup. It is kind of similar... Along with Wayne Chang&#039;s comment: consider the current flow of readers from Digg to Reddit: a flow towards simplicity.

@John: Debt consolidation would be perfect (mathematically, economically and psychologically) if the interest rate they offered was not as high as currently offer. But of course, a lot of people needing debt consolidation may end up not paying, and the company has to enable some money recouping system.

Cheers, 

Ruben]]></description>
		<content:encoded><![CDATA[<p>I wasn&#8217;t aware from that quote from Stroustrup. It is kind of similar&#8230; Along with Wayne Chang&#8217;s comment: consider the current flow of readers from Digg to Reddit: a flow towards simplicity.</p>
<p>@John: Debt consolidation would be perfect (mathematically, economically and psychologically) if the interest rate they offered was not as high as currently offer. But of course, a lot of people needing debt consolidation may end up not paying, and the company has to enable some money recouping system.</p>
<p>Cheers, </p>
<p>Ruben</p>
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		<title>By: Wayne Chang</title>
		<link>http://www.johndcook.com/blog/2010/11/02/snowball-strategy/comment-page-1/#comment-18136</link>
		<dc:creator>Wayne Chang</dc:creator>
		<pubDate>Tue, 02 Nov 2010 15:07:20 +0000</pubDate>
		<guid isPermaLink="false">http://www.johndcook.com/blog/?p=6955#comment-18136</guid>
		<description><![CDATA[The best example of this is....craigslist. Everyone criticizes it but its very simplicity is one of the major factors in growth.]]></description>
		<content:encoded><![CDATA[<p>The best example of this is&#8230;.craigslist. Everyone criticizes it but its very simplicity is one of the major factors in growth.</p>
]]></content:encoded>
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		<title>By: John</title>
		<link>http://www.johndcook.com/blog/2010/11/02/snowball-strategy/comment-page-1/#comment-18135</link>
		<dc:creator>John</dc:creator>
		<pubDate>Tue, 02 Nov 2010 15:02:37 +0000</pubDate>
		<guid isPermaLink="false">http://www.johndcook.com/blog/?p=6955#comment-18135</guid>
		<description><![CDATA[Debt consolidation could be a good idea mathematically and psychologically. You may be able to reduce both the number of loans and the interest rate at the same time.]]></description>
		<content:encoded><![CDATA[<p>Debt consolidation could be a good idea mathematically and psychologically. You may be able to reduce both the number of loans and the interest rate at the same time.</p>
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		<title>By: Nirmal Patel</title>
		<link>http://www.johndcook.com/blog/2010/11/02/snowball-strategy/comment-page-1/#comment-18134</link>
		<dc:creator>Nirmal Patel</dc:creator>
		<pubDate>Tue, 02 Nov 2010 14:56:22 +0000</pubDate>
		<guid isPermaLink="false">http://www.johndcook.com/blog/?p=6955#comment-18134</guid>
		<description><![CDATA[I know the point wasn&#039;t to give financial advice but this post makes me wonder if &quot;debt consolidation&quot; services actually try to use your monthly payment in a mathematically optimal way. I would hope the answer is yes but the part of me that has seen corporate greed is pessimistic.]]></description>
		<content:encoded><![CDATA[<p>I know the point wasn&#8217;t to give financial advice but this post makes me wonder if &#8220;debt consolidation&#8221; services actually try to use your monthly payment in a mathematically optimal way. I would hope the answer is yes but the part of me that has seen corporate greed is pessimistic.</p>
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		<title>By: Ross Smith</title>
		<link>http://www.johndcook.com/blog/2010/11/02/snowball-strategy/comment-page-1/#comment-18133</link>
		<dc:creator>Ross Smith</dc:creator>
		<pubDate>Tue, 02 Nov 2010 14:50:04 +0000</pubDate>
		<guid isPermaLink="false">http://www.johndcook.com/blog/?p=6955#comment-18133</guid>
		<description><![CDATA[I&#039;m reminded of something Bjarne Stroustrup, designer of C++, once said: &quot;There are two kinds of programming languages: the ones everybody complains about, and the ones nobody uses.&quot;]]></description>
		<content:encoded><![CDATA[<p>I&#8217;m reminded of something Bjarne Stroustrup, designer of C++, once said: &#8220;There are two kinds of programming languages: the ones everybody complains about, and the ones nobody uses.&#8221;</p>
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		<title>By: Rob Lempke</title>
		<link>http://www.johndcook.com/blog/2010/11/02/snowball-strategy/comment-page-1/#comment-18132</link>
		<dc:creator>Rob Lempke</dc:creator>
		<pubDate>Tue, 02 Nov 2010 14:49:04 +0000</pubDate>
		<guid isPermaLink="false">http://www.johndcook.com/blog/?p=6955#comment-18132</guid>
		<description><![CDATA[I often find myself tackling small bugs and feature first before large ones when maintaining code; probably for the same reason.]]></description>
		<content:encoded><![CDATA[<p>I often find myself tackling small bugs and feature first before large ones when maintaining code; probably for the same reason.</p>
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		<title>By: Ruben Berenguel</title>
		<link>http://www.johndcook.com/blog/2010/11/02/snowball-strategy/comment-page-1/#comment-18131</link>
		<dc:creator>Ruben Berenguel</dc:creator>
		<pubDate>Tue, 02 Nov 2010 14:46:35 +0000</pubDate>
		<guid isPermaLink="false">http://www.johndcook.com/blog/?p=6955#comment-18131</guid>
		<description><![CDATA[This is like the &quot;mental relativity&quot; effects, and why prices are always x.95 or x.99. Our mind just adjusts the price to the lower bound... Psychologically correct, mathematically (or financially) incorrect. But as a mathematician, I hope that you are not in deep enough debt to need a snowball effect and can instead work with a mathematically better model :)

Cheers, 

Ruben
Latest in my blog: &lt;a href=&quot;http://www.mostlymaths.net/2010/10/30-best-posts-i-have-read-this.html&quot; rel=&quot;nofollow&quot;&gt;30 Best Posts I Have Read This September, 2010&lt;/a&gt;]]></description>
		<content:encoded><![CDATA[<p>This is like the &#8220;mental relativity&#8221; effects, and why prices are always x.95 or x.99. Our mind just adjusts the price to the lower bound&#8230; Psychologically correct, mathematically (or financially) incorrect. But as a mathematician, I hope that you are not in deep enough debt to need a snowball effect and can instead work with a mathematically better model <img src='http://www.johndcook.com/blog/wp-includes/images/smilies/icon_smile.gif' alt=':)' class='wp-smiley' /> </p>
<p>Cheers, </p>
<p>Ruben<br />
Latest in my blog: <a href="http://www.mostlymaths.net/2010/10/30-best-posts-i-have-read-this.html" rel="nofollow">30 Best Posts I Have Read This September, 2010</a></p>
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		<title>By: gregory</title>
		<link>http://www.johndcook.com/blog/2010/11/02/snowball-strategy/comment-page-1/#comment-18130</link>
		<dc:creator>gregory</dc:creator>
		<pubDate>Tue, 02 Nov 2010 14:45:07 +0000</pubDate>
		<guid isPermaLink="false">http://www.johndcook.com/blog/?p=6955#comment-18130</guid>
		<description><![CDATA[Part of the problem is software usually doesn&#039;t contain these constraints so no outsider can possibly know why software is what it has become.]]></description>
		<content:encoded><![CDATA[<p>Part of the problem is software usually doesn&#8217;t contain these constraints so no outsider can possibly know why software is what it has become.</p>
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		<title>By: Tweets that mention Mathematically correct but psychologically wrong -- Topsy.com</title>
		<link>http://www.johndcook.com/blog/2010/11/02/snowball-strategy/comment-page-1/#comment-18129</link>
		<dc:creator>Tweets that mention Mathematically correct but psychologically wrong -- Topsy.com</dc:creator>
		<pubDate>Tue, 02 Nov 2010 14:30:20 +0000</pubDate>
		<guid isPermaLink="false">http://www.johndcook.com/blog/?p=6955#comment-18129</guid>
		<description><![CDATA[[...] This post was mentioned on Twitter by John D. Cook, Richard Minerich, Todd Buckley, Todd Buckley, Bradley Heath and others. Bradley Heath said: RT @JohnDCook: Mathematically correct but psychologically wrong http://bit.ly/dmTLGF [...] ]]></description>
		<content:encoded><![CDATA[<p>[...] This post was mentioned on Twitter by John D. Cook, Richard Minerich, Todd Buckley, Todd Buckley, Bradley Heath and others. Bradley Heath said: RT @JohnDCook: Mathematically correct but psychologically wrong <a href="http://bit.ly/dmTLGF" rel="nofollow">http://bit.ly/dmTLGF</a> [...] </p>
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