About the 4% Rule
I want to write about the 4% rule which has become the rule
of thumb approach for many regarding retirement income planning.
What is the 4% rule? It is the rule that says a retiree can
take 4% of their retirement nest-egg, with an inflation-adjusted increase each
year thereafter, with a very high probability of not running out of money. So, a retiree can safely withdraw $40,000 in
year one of retirement from his $1 million nest-egg, and ratchet that $40,000
up 3% each year thereafter to cover cost-of-living increases.
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There are many questions to ask before applying this rule in retirement. Some of the more obvious ones would be:
- What are the underlying investment returns and volatility?
- Over what time period can this rising (inflation-adjusted) income be
withdrawn?
- How much money will be left of the nest-egg after the retirement period in question?
The 4% rule is based on the safe withdrawal rate strategy of managing sequence-of-returns risk (sometimes called sequence risk) which attempts to manage spending conservatively such that even a bear market in stocks early in retirement will not deplete the retiree’s capital.
William Bengen’s study in the October 1994 Journal of Financial Planning was ground-breaking in focusing on the sequence of returns’ impact on withdrawal rates. Wade Pfau, Ph. D., CFA retirement researcher has used Bengen’s historical data to show the lowest safe withdrawal rate over rolling 30-year periods from 1926 to 2016, using a 50%/50% stock/bond allocation, was in 1966 with the SAFEMAX at 4.15% (4.7% on average).
(Note: The early years of this 30-year period had market losses which caused the portfolio’s premature depletion. Had the average return for the period been constant each year, a 5.9% withdrawal rate would have been possible. This emphasizes the significance of the sequence of returns. Low returns/losses hurt the retiree much more in the early years of retirement than in the later years (as far as the money lasting). Think of sequence risk loss as reverse dollar cost averaging. When investing for retirement, the lower the prices, the more shares you buy , which is good. In withdrawing in retirement, the lower the prices, the more shares you sell , which is bad--especially if it is early in retirement.)
Following Bengen, the Trinity Study article in the February 1998 issue of the Journal of the Association of Individual Investors focused on success rates over different allocations and different time periods. Their study, using the same historical data as Bengen (except for different bond indexes) led people to think that the 4% rule for 30 years would provide a 95% probability of success; thus giving further credibility to the rule of thumb.
As planners continued this research, Monte Carlo simulations began to be used instead of historical simulations. The advantage is that Monte Carlo simulations provide a much wider range of possible future scenarios. Unlike the original studies, Monte Carlo studies show that bond-heavy portfolios have success rates of over 90%, with the optimum stock allocation being between 30 and 60%.
This gives you just a little of the history of retirement income research. For the sake of brevity, let’s list some of the major assumptions of the 4% rule, with some reasons for caution.
1. The 4% rule was for 30 years . The 4% rule never applied to older retirees in their 80s who could take a higher withdrawal rate--or younger retirees in their 40s and 50s who would have a much higher probability of running out of money using a 4% rate.2. It was based on 1926 to 2016 historical simulations . There is no good reason to think these limited historical scenarios represent the full range of possible futures. Monte Carlo simulations are much better at covering a larger and random set of scenarios. Also, the studies only used large-cap U.S. stock returns (the S&P 500 index) during which time the U.S. market generally had strong returns . With current U.S. stock valuations at high levels and interest rates at near-historic lows, the same type of investments may not produce the returns that can sustain a 4% rate for 30 years.
3. It did not consider a safety margin . The 4% rule did not factor in a safety margin toward the end of life, or retirees desiring to leave an inheritance. Most retirees do not want to see their nest-egg falling so sharply as the 30-year period ends—especially in light of the fact they may live longer than 30 years. Along with "probability of success" is also how much of the assets remain in case they live longer.
4. It assumed spending continually increases in retirement . In reality, the more likely spending scenario looks like a bathtub curve or smile. Retirees often spend more in their early retirement years, and then spend less as they become less active, and then typically spend more again toward the end of life due to health care.
5. It assumed a flat glide path of 50 to 75% in stocks . Depending on the use of broader diversification, a dynamic versus completely flat glide path, and a retiree’s resistance to high volatility, the 4% safe withdrawal rate could be higher or lower than 4%.
The story continues beyond the pioneers like Bengen, the Trinity Study, and the use of Monte Carlo simulations. Variable spending strategies emerged which allow guidance rules that can keep a retiree on track in the midst of unpredictable future returns. For more, see my article Three Steps to Safely Maximize Your Portfolio Income .
Conclusion
No retiree should blindly use the 4% rule for retirement income planning. There are too many assumptions that do not necessarily apply today. It is best that each retiree creates their own personal road-map based on their own unique goals and situation. The sustainable withdrawal rate could be higher or lower. It may end up being 4%, but that should be demonstrated, not merely assumed. And it may be that the 4% rate can be achieved with much less volatility risk than the rule initially prescribed.
Travis Echols , CRPC®, CSA
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