What is the Standard Deviation of the PP?

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Xtal
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What is the Standard Deviation of the PP?

Post by Xtal »

Hi all,

I've been obsessing over Firecalc http://firecalc.com/ -- You can plug in all kinds of numbers, and it tells you the odds of your retirement stash going to 0.

Anyway, there's a tab where you can plug in your own investment strategy.  One of the options is:
A portfolio with random performance, with a mean total portfolio return of __% and variability (standard deviation) of __%. Assume an inflation rate of __%.
I can find good numbers for the mean return and for inflation, but what number would you plug in for the standard deviation?

Thanks.
Xtal
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Re: What is the Standard Deviation of the PP?

Post by Xtal »

Anyone? Bueller?  I tried searching online but found several different numbers.
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MachineGhost
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Re: What is the Standard Deviation of the PP?

Post by MachineGhost »

1975-2012: 8.85% CAGR, 7.81% SD, 3.9933% CPI.
Last edited by MachineGhost on Sun Feb 24, 2013 1:23 pm, edited 1 time in total.
"All generous minds have a horror of what are commonly called 'Facts'. They are the brute beasts of the intellectual domain." -- Thomas Hobbes

Disclaimer: I am not a broker, dealer, investment advisor, physician, theologian or prophet.  I should not be considered as legally permitted to render such advice!
Xtal
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Re: What is the Standard Deviation of the PP?

Post by Xtal »

Thanks MachineGhost!
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Tyler
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Re: What is the Standard Deviation of the PP?

Post by Tyler »

I've also been obsessed with Firecalc.  Rediscovered this thread last night and had a thought.

If we look at the real returns (after inflation), the performance from 1975-2012 is 4.76% CAGR, 6.84% SD.  While that reflects the same overall 4% inflation rate in the CAGR that MachineGhost references, the SD is a little lower.  I assume this is because PP performance is certainly not random relative to inflation -- the gold responds quite strongly.  As a result, the other thing I find fascinating is that the real returns are quite consistent across a variety of timeframes:

CAGR since 1975 is 8.81 nominal, 4.76 real
CAGR since 1990 is 7.56 nominal, 5.03 real

So here's the thing -- if you use the PP real return numbers in Firecalc and set inflation to zero accordingly, not only do I think that reflects performance more accurately, but also it appears to improve results slightly.  (Note that Firecalc can give vastly different results run-to-run with the random number generator, so run it several times to see the range).

Unless, of course, I'm doing it all wrong.  ;)

TL;DR : Try the PP real returns as I think they're more appropriate for the tool.  4.76% CAGR, 6.84% SD, 0% inflation

[Edited for clarity]
Last edited by Tyler on Wed May 15, 2013 11:08 am, edited 1 time in total.
Khisanth
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Re: What is the Standard Deviation of the PP?

Post by Khisanth »

But then doesn't that mean your spending is not tracking inflation in the FireCalc calculation?

EDIT: No, it doesn't. The Spending tab has an inflation tracking percentage adjustment separate from the Portfolio tab.
Last edited by Khisanth on Wed May 15, 2013 6:53 pm, edited 1 time in total.
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