Originally posted by TrunkMonkey
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Here are two monte carlo simulators (free) online which I use:
Flexible Retirement Planner
that is the best tool I use, but its complicated until you run it a few times and compare results.
FIRECalc: A different kind of retirement calculator
on the surface firecalc is simpler. Realize each tab is an option to give further detail
Here is an example I ran thru firecalc
spending 50k
portfolio 1250000
years 50
spending model (constant spending power)- this is default, but review other choices- there is an option here to test the 94/6 you suggested in an earlier post
portfolio is total market- notice you can identify the returns and deviations... realize the deviations are what a monte carlo is doing for you.
The results
FIRECalc looked at the 90 possible 50 year periods in the available data, starting with a portfolio of $1,250,000 and spending your specified amounts each year thereafter.
Here is how your portfolio would have fared in each of the 90 cycles. The lowest and highest portfolio balance throughout your retirement was $-2,511,798 to $22,109,613, with an average of $4,884,547. (Note: values are in terms of the dollars as of the beginning of the retirement period for each cycle.)
For our purposes, failure means the portfolio was depleted before the end of the 50 years. FIRECalc found that 13 cycles failed, for a success rate of 85.6%.
Here is how your portfolio would have fared in each of the 90 cycles. The lowest and highest portfolio balance throughout your retirement was $-2,511,798 to $22,109,613, with an average of $4,884,547. (Note: values are in terms of the dollars as of the beginning of the retirement period for each cycle.)
For our purposes, failure means the portfolio was depleted before the end of the 50 years. FIRECalc found that 13 cycles failed, for a success rate of 85.6%.
Does an Actuary need to know how to read? Some of this was explained earlier in this thread, but you did not read it, or did not understand it.
4% rule and constant spending power mean this
If withdraw in year 1 is 4%- 50k in above example
year 2 it is 4%+3% (so 50k plus 3%) which is $51500 ($1500 increase is 3% and this accounts for inflation).
Year 2 it is 4% +3%+3%. This means it is $51500+3%=$53045.
fast forward to year 24 (so 24 3% increases) and the withdraw is $101,640
In year 1, $50,000 of $1,250,000 was withdrawn. In year 24 $101,640 of the initial $1,250,000 is taken (this is an 8% withdraw relative to initial value).
What is happening is the portfolio is returning some return and this return is changing every year. In general the trend should be "up". So year 1 4% is taken out and 6% is returned by the market. Year 2 4%+3% is taken out and market might return -8%, this return scheme continues until person dies (then it continues for whoever inherits the assets). The 4& initial withdraw and 3% inflation increments eventually mean the person taking money out will be taking out more than an 8% nominal makret return provides (year 24 in the example I listed).
What a monte carlo does is show you based on PAST PERFORMANCE how successful a strategy would be, and the primary output of the monte carlo is the percentage (not the spending pattern).
An annuity MIGHT be able to tell me to retire with a "7% withdraw rate" at start of retirement, but by year 24 that withdraw needs to be twice as high. By year 48 it needs to be 4 times as high (to maintain constant spending power).
The planning with the 4% rule is this-when I chose the total market option above, I probably chose something which was like 100% equities (use total stock market index). Way too much risk- but my success rate for a 50 year period was high.
I'd much prefer to have a 40-60 portfolio, so for that I use the other tool. I changed inputs and received a 67% success rate. This means I save more, change assumptions, or change spending pattern.
This is level of research needed for 4%- its not as simple as set it and forget it- spending behavior is key to planning for it, as well as knowing success rate (some people want 100% success rate, and I am happy with anything above 80%). Its about the risks we take...
For example if I change inflation from 3.5% to 2.5% my success rate goes from 69% to 89%. Inflation is the single biggest factor to success- whether with annuity or 4% rule.

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