Lsbcal
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Test of constant % spending model + reserve fund
I wanted to test out how a constant percentage spending model would work under a worst case historical sequence. I used VPW to show the historical simulation results and to suggest a way to deploy a short term reserve account. I'm showing some results here because I'd like to hear if someone sees flaws in the approach. This is pretty detailed and the example is commented to help out a bit. Sorry about this but please ask questions if I can help to clear up confusion.
What I did was to use the VPW withdrawal algorithm to compute allowed spending each year. VPW by itself results in some very high withdrawals with the possibility one would have to cut spending in some later years until the portfolio recovers. It does have the advantage of never entirely running out of money over the sequence (up to the Depletion Years number). Since we personally do not need so much to spend I assumed we would put the excess into a short term reserve fund that just keeps up with inflation. This reserve then fills in the needs further into a very bad sequence and would be available should the bad sequence not happen at all. This reserve fund approach is used by some of our esteemed forum members and I like the idea.
Below is an example which shows how the short term reserve grows and then shrinks. The blue columns are my additions to show the way the reserve fund works. This is for a fictitious couple who are 65 and draw social security ($34000) with a 60/40 portfolio and a $1M starting value. The portfolio must last to age 110 i.e. there will be some money left over for heirs and no danger of serious worrisome depletion. The worst case postwar sequence starting in 1966 was used. The couple was assumed to spend $65000 inflation adjusted each year. This works out to a 3.1% withdrawal rate from the portfolio which happens to be close to our personal withdrawal rate for the last 3 years.
The detailed results are shown below. I've removed charts from the VPW backtest sheet and added some columns to show the reserve fund and the total portfolio value each year. In this simulation you can see the years when the reserve fund was needed (red negative values in the "unspent, goes to reserves" column). The worst case inflation corrected portfolio value occurred 17 years into the simulation at 44% of the start value. By age 90 the portfolio recovers to 55% of the start value and by age 100 the portfolio recovers to 84% of the start value.
Clearly there is some room to dynamically adjust spending if the bad sequence is not showing up or if the sequence is even worse then 1966. The sequence starting in 1964 has a much more comforting outcome. The 16 years since the year 2000 also is much better.
The fact that a 3.1% withdrawal rate works in a 60/40 portfolio will probably surprise nobody here. But I like the fact that I can see how the sequence unfolds and adjust some input parameters at will.
I wanted to test out how a constant percentage spending model would work under a worst case historical sequence. I used VPW to show the historical simulation results and to suggest a way to deploy a short term reserve account. I'm showing some results here because I'd like to hear if someone sees flaws in the approach. This is pretty detailed and the example is commented to help out a bit. Sorry about this but please ask questions if I can help to clear up confusion.
What I did was to use the VPW withdrawal algorithm to compute allowed spending each year. VPW by itself results in some very high withdrawals with the possibility one would have to cut spending in some later years until the portfolio recovers. It does have the advantage of never entirely running out of money over the sequence (up to the Depletion Years number). Since we personally do not need so much to spend I assumed we would put the excess into a short term reserve fund that just keeps up with inflation. This reserve then fills in the needs further into a very bad sequence and would be available should the bad sequence not happen at all. This reserve fund approach is used by some of our esteemed forum members and I like the idea.
Below is an example which shows how the short term reserve grows and then shrinks. The blue columns are my additions to show the way the reserve fund works. This is for a fictitious couple who are 65 and draw social security ($34000) with a 60/40 portfolio and a $1M starting value. The portfolio must last to age 110 i.e. there will be some money left over for heirs and no danger of serious worrisome depletion. The worst case postwar sequence starting in 1966 was used. The couple was assumed to spend $65000 inflation adjusted each year. This works out to a 3.1% withdrawal rate from the portfolio which happens to be close to our personal withdrawal rate for the last 3 years.
The detailed results are shown below. I've removed charts from the VPW backtest sheet and added some columns to show the reserve fund and the total portfolio value each year. In this simulation you can see the years when the reserve fund was needed (red negative values in the "unspent, goes to reserves" column). The worst case inflation corrected portfolio value occurred 17 years into the simulation at 44% of the start value. By age 90 the portfolio recovers to 55% of the start value and by age 100 the portfolio recovers to 84% of the start value.
Clearly there is some room to dynamically adjust spending if the bad sequence is not showing up or if the sequence is even worse then 1966. The sequence starting in 1964 has a much more comforting outcome. The 16 years since the year 2000 also is much better.
The fact that a 3.1% withdrawal rate works in a 60/40 portfolio will probably surprise nobody here. But I like the fact that I can see how the sequence unfolds and adjust some input parameters at will.
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