A new way to calculate how much you can spend in retirement
How much can you afford to spend in retirement?
Most retirement withdrawal calculators approach this question by starting with a withdrawal rate. You select a percentage of your portfolio, perhaps 4%, and the calculator estimates how likely your money is to last throughout retirement.
But this approach makes an important assumption: that your spending will remain constant in real terms throughout retirement.
In reality, retirement spending is rarely that simple. You might want to spend more during your early retirement years when you are active and have more opportunities to travel. You might prefer to reduce spending later, or reserve more of your portfolio for your heirs. You might even plan to add money back to your portfolio during certain years.
Your retirement lifestyle is unique. Why should your withdrawal strategy be based on a fixed spending assumption?
Princeton Asset introduces the Lifestyle Withdrawal Rate (LWR), a new approach to retirement withdrawal planning that starts with your retirement spending preference throughout retirement and then calculates the initial withdrawal rate your portfolio can support such that the terminal portfolio value is above a set bequest ratio (percentage of initial amount left as inheritance) over the chosen time horizon.
Rather than asking whether a particular withdrawal rate will work, the Lifestyle Withdrawal Rate asks a different question:
Given the lifestyle I want to maintain throughout retirement, how much can I initially withdraw from my portfolio?
What Is the Lifestyle Withdrawal Rate?
The Lifestyle Withdrawal Rate (LWR) is the initial portfolio withdrawal rate that, given a specified sequence of portfolio returns, produces a terminal portfolio value equal to the required bequest ratio after following your expressed annual retirement spending preferences over the selected time horizon.
The bequest ratio represents the desired ending portfolio value as a percentage of the initial portfolio, to be left as inheritance.
In other words, the LWR is the initial withdrawal rate that allows you to follow your preferred spending pattern throughout retirement while meeting your specified bequest target, given a particular sequence of portfolio returns.
1. Define Your Retirement Lifestyle Parameters
The starting point is choosing the time horizon and a bequest ratio. The time horizon is the projected length of the retirement period and the bequest ratio represents the percentage of the initial portfolio value, in real today’s money, that you intend to leave as inheritance.
Then, instead of a fixed spend amount per year, choose a relative annual spending preference.
Princeton Asset allows you to specify a relative spending preference for every year of retirement. The first year is normalized to 100%, and every subsequent year represents your desired real spending relative to that initial reference.
For example, consider the following retirement spending preference:
| Retirement year | Spending preference |
|---|---|
| 1 | 100% |
| 2 | 120% |
| 3 | 115% |
| 5 | 110% |
| 10 | 100% |
| 15 | 90% |
| 20 | 80% |
| 25 | 70% |
| 30 | 60% |
This represents someone who wants to spend more during the early years of retirement and gradually reduce spending over time.
You can create virtually any spending pattern by adjusting the annual preferences.
For example, you might prefer:
- Front-loaded spending: Spend more during the early retirement years and less later.
- Back-loaded spending: Begin retirement conservatively and increase spending over time.
- Declining spending: Gradually reduce real spending as retirement progresses.
- Increasing spending: Plan for higher spending in later years.
- Variable spending: Specify different spending levels for individual years based on anticipated lifestyle changes.
There is no requirement to follow a predetermined spending pattern. You define the lifestyle you want to model.
Negative Spending Preferences
An additional feature is the ability to specify negative spending preferences.
A positive preference represents a portfolio withdrawal. A negative preference represents a contribution to the portfolio.
For example, a preference of -20% means that the portfolio receives a contribution equal to 20% of the initial spending reference amount in today’s money.
This allows you to model retirement strategies that include both portfolio withdrawals and contributions.
The result is a flexible cash-flow preference that can accommodate a much broader range of retirement lifestyles than conventional withdrawal calculators.
2. Monte Carlo Simulations
Once your retirement lifestyle parameters are set, the Monte Carlo engine evaluates lifestyle withdrawal rates against ten thousand possible portfolio return paths.
Why is this important?
Investment returns are unpredictable, and their sequence matters.
Consider two retirees who experience the same average annual investment return over 30 years. One experiences strong returns early in retirement, while the other experiences substantial losses during the first several years.
Even though their average returns are identical, their ending portfolio values can be dramatically different.
This is known as sequence-of-returns risk (SORR).
When you are withdrawing money from a portfolio, poor returns early in retirement can have a disproportionately negative effect. You may be forced to sell investments at depressed prices to fund spending, leaving fewer assets available to participate in a subsequent market recovery.
Monte Carlo simulation addresses this uncertainty by evaluating many different sequences of investment returns rather than relying on one historical period or a constant average return.
For each simulated portfolio path, the model evaluates the lifestyle withdrawal rate at which the portfolio can support your specified spending preferences and satisfy the required ending portfolio value over the time horizon.
For each simulated portfolio path, we calculate the corresponding Lifestyle Withdrawal Rate (LWR). We then aggregate the results across all simulations to construct a cumulative distribution of LWRs. This distribution allows us to estimate the portfolio failure rate for any selected LWR – that is, the percentage of simulated portfolio paths in which the portfolio fails to meet the specified spending preferences and target bequest ratio.
3. Choose Your Lifestyle Withdrawal Rate
For example, suppose you have a $1 million portfolio and want to evaluate a 30-year retirement.
You specify a spending preference that calls for higher spending during the first five years, followed by gradually declining real spending.
The Monte Carlo simulation evaluates this strategy across thousands of possible portfolio paths.
Rather than testing only a fixed 4% initial withdrawal rate, the model determines the sustainable lifestyle withdrawal rate for each of the simulated outcomes.
You can then examine the distribution of those rates and the corresponding failure probabilities.
For example, you might consider a lifestyle initial withdrawal rate of 3.5% because it is associated with a 5% failure probability.
The important distinction is that this result is conditional on your spending preference, time horizon and bequest ratio. Change any of those, and the calculated lifestyle withdrawal rate changes accordingly.
This is what makes our Lifestyle Withdrawal Rate different from conventional safe withdrawal rate analysis.
4. Understand the Results
The Princeton Asset Monte Carlo Withdrawal Simulation provides several ways to examine the results.
Outcome Distribution
The outcome distribution displays the frequency of lifestyle withdrawal rates across the Monte Carlo simulations.
A histogram shows how frequently different lifestyle withdrawal rates occur, while a cumulative failure-rate curve shows the relationship between the lifestyle withdrawal rate and the proportion of simulations that fail to satisfy the required conditions.
This allows you to evaluate the risk associated with different lifestyle withdrawal rates.
Rather than relying on a single LWR/failure rate result, you can examine the entire distribution of possible outcomes.
Withdrawal Paths
The Withdrawal Paths chart displays how portfolio values evolve throughout retirement across the simulated portfolio scenarios.
Percentile withdrawal paths show the range of possible portfolio outcomes, for the median and upper/lower percentile return paths.
This helps illustrate the uncertainty surrounding future portfolio values and the impact of different portfolio sequences.
Cumulative Real Growth
The Cumulative Real Growth chart provides another perspective on portfolio performance.
It shows the distribution of cumulative portfolio growth, adjusted for inflation, relative to the initial portfolio value.
This makes it easier to understand the range of potential long-term portfolio outcomes in purchasing-power terms.
Together, these charts provide a more comprehensive view of retirement sustainability than a single withdrawal-rate calculation.
5. Evaluate Different Retirement Lifestyles
One of the most useful applications of the Lifestyle Withdrawal Rate is comparing different spending strategies.
You can start with a constant real spending preference and then modify it to reflect your desired lifestyle.
For example:
Strategy A: Constant Spending
Maintain the same real spending throughout retirement.
Strategy B: Front-Loaded Spending
Spend more during the first ten years and gradually reduce spending afterward.
Strategy C: Declining Spending
Reduce real spending incrementally throughout retirement.
Strategy D: Spending Smile
Create a personalized spending trajectory that reflects the average retiree spending pattern.
You can compare the resulting withdrawal-rate distributions and failure probabilities to understand how different spending preferences affect portfolio sustainability.
You can also change the simulation horizon and required bequest ratio to examine how these assumptions affect the results.
This provides a practical way to explore the trade-offs between current spending, future spending, portfolio sustainability, and wealth preservation and to review your retirement plans every year as circumstances change.
6. Why the Lifestyle Withdrawal Rate Is Different
Traditional safe withdrawal rate research generally focuses on determining a fixed initial withdrawal percentage that can be adjusted for inflation throughout retirement.
The familiar 4% rule is an example of this approach.
Monte Carlo calculators have expanded the analysis by evaluating withdrawal strategies across many possible investment return sequences.
However, using Monte Carlo simulation does not necessarily solve the underlying limitation of fixed real spending assumptions.
The Lifestyle Withdrawal Rate changes the question.
Instead of starting with a withdrawal percentage and asking whether it is sustainable, it starts with the desired spending pattern and bequest ratio and calculates the lifestyle withdrawal rate that can support it.
This distinction is important because retirement is not simply a 30-year exercise in withdrawing the same inflation-adjusted amount.
It is about financing a lifestyle that may change considerably over time.
The ability to specify an arbitrary annual spending preference, including periods of portfolio contributions, makes the Lifestyle Withdrawal Rate a flexible framework for evaluating retirement cash-flow scenarios.
Try the Lifestyle Withdrawal Rate with Princeton Asset
There is no single retirement spending pattern that works for everyone.
Some retirees want to maximize spending while they are young and active. Others prefer a more conservative approach, with greater emphasis on preserving wealth for later years or leaving an inheritance.
Your withdrawal strategy should reflect those preferences.
Princeton Asset’s Lifestyle Withdrawal Rate Simulator lets you define your preferred retirement spending pattern and uses thousands of Monte Carlo simulations to generate a cumulative distribution of Lifestyle Withdrawal Rates (LWRs). The resulting distribution shows the relationship between withdrawal rates and portfolio failure rates, allowing you to evaluate the trade-offs across the full range of outcomes.
Set your ideal retirement lifestyle parameters first – then use the simulator to model withdrawal rate vs. portfolio failure rate trade-offs.
To start: create a portfolio backtest model then scroll down to test run our Lifestyle Withdrawal Simulator.
Disclaimer: This blog post is for informational purposes only and should not be considered financial advice. Past performance is not a guarantee of future results. Consult with a qualified financial advisor for personalized guidance.
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