Differences between old and new

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Joined: Sun Aug 30, 2015 4:38 pm

Differences between old and new

Postby eyeofthefrog » Thu Sep 03, 2015 5:18 am


In the previous tool, my inputs (ID:84462) result in the following:
Success Rate: 96.39%
Average Portfolio at Retirement: $1,286,662.82
Average Ending Portfolio: $18,902,265.31

Using the same inputs in the new tool results in:
Success Rate: 97.56%
Average Portfolio at Retirement: $1,475,370
Average Ending Portfolio: $5,096,282

I've tried to go back and forth to figure out if I didn't type a year correctly and couldn't find anything. I'm still open to the fact it is my fault and I missed something. :) Is this expected with some of the changes?


PS. Should I put things like this as an issue in github?

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Re: Differences between old and new

Postby bo_knows » Fri Sep 04, 2015 11:55 am

There are a few slight differences between the old and new, but that average ending portfolio difference seems large.

The biggest difference is how spending is taken out. In the old cFIREsim for any given year, here is how things are calculated:

- Jan 1 - Portfolio $X
- Dec 31st - Portfolio $X + Market Gains - Spending

The new version, takes spending out on January 1st (which most people seem to think is more intuative to how people would actually withdrawal) and thus that amount doesn't necessarily get the benefit of market gains. So, it's like:

- Jan 1st - Portfolio = $X - Spending
- Dec 31st - Portfolio = (Above amount) + Market gains.

This might be a little too specific to put as a bug on github, but let me look at the year-to-year differences to see if anything is out of place.
-Bo (Creator and Admin for cFIREsim)

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