狮山巡礼
投资杂谈
This is a classic dilemma for retirees, and it touches on the fundamental conflict between maximizing growth and minimizing risk when you are actively drawing down your portfolio.
Here is a simulation and analysis of the two approaches, focusing on the long-term perspective (25-30+ years of retirement).
The Critical Risk: Sequence of Returns Risk
In the long run, Scenario 1 (100% SPY) has the highest mathematical chance of producing the largest average final portfolio value. The SP 500 has historically been the best long-term growth engine.
However, in retirement, the sequence of returns matters more than the average return. This is why Scenario 1 is generally considered more dangerous.
Sequence of Returns Risk Explained
Imagine you retire in year 1.
Scenario 1: The market immediately drops by 25% in year 1. Since you are 100% in stocks, your entire portfolio drops by 25%. When you sell a portion to cover your annual expenses, you are selling low, and you have to sell more shares to get the cash you need. This dramatically damages your portfolios ability to recover when the market eventually turns around. This early, severe drawdown can lead to the portfolio running out of money much sooner than a balanced portfolio, despite the 100% stock portfolio having a higher average return over a 30-year period.
Scenario 2: The market drops by 25% in year 1. Your 80% stock portion drops, but your 20% safety portion holds its value (or drops less). To cover your expenses, you first draw from the safety portion, not the beaten-down stocks. This gives your stock component time to recover without being forced to sell at a loss, significantly lowering the risk of a premature portfolio depletion.
???? Conclusion: Which is Better in the Long Run?
In the context of retirement withdrawal (selling for cash flow), Scenario 2 (80/20) is generally better and safer in the long run for most retirees who need a reliable income stream.
Why Scenario 2 is Safer:
1. Mitigates Sequence of Returns Risk: This is the most important factor. The safety portion acts as a buffer. You draw from it during market downturns, giving your growth assets (SPY) a chance to recover. This greatly improves the portfolios survival rate over a 30-year horizon.
2. Reduces Behavioral Risk: Retirees facing a 30-40% market crash in their first few years are more likely to panic, stop their withdrawals, or make other emotionally driven mistakes. A less volatile 80/20 portfolio is easier to stick with, which is critical for long-term success.
When Scenario 1 Might be Better:
Scenario 1 is better only if:
1. You have a very long time horizon AND an extremely high-risk tolerance: You are comfortable with the portfolio potentially losing 50% of its value and you absolutely do not need to touch that money for many years.
2. Your withdrawal rate is extremely low: If you are only withdrawing 1-2% annually, the risk is diminished, and you will likely end up with the highest terminal value.
3. You have a massive pension or other income: If your expenses are almost entirely covered by a non-portfolio income source (e.g., a large pension or Social Security), and the portfolio is simply extra, the aggressive approach is more feasible.
Would you like me to compare the estimated 30-year success rate of a fixed 4% annual withdrawal for both the 100% SPY and the 80/20 portfolio?
We will use the widely referenced 4% Safe Withdrawal Rate (SWR) Rule as our benchmark. This rule states that if you withdraw 4% of your initial portfolio value in year one, and then increase that dollar amount by inflation every subsequent year, your portfolio has a high chance of lasting 30 years.
Here is a comparison of the 30-year success rates based on historical simulations (often referred to as the Trinity Study and its updates):
1. Scenario 1: 100% SPY (Aggressive)
Success Rate: Historically, the success rate for 100% stocks is very high, often cited as 95% to 98% for a 30-year period using a 4% SWR.
The Upside: The years that succeed, succeed massively. The median remaining portfolio after 30 years is significantly higher than any other allocation.
The Downside (The Failure): The 2-5% chance of failure is catastrophic. This failure happens when you retire just before a prolonged bear market (e.g., retiring in 1929, or 1968-1972). Because you have no stable assets, you are forced to sell deeply depressed stocks for your income, severely damaging the long-term compounding. This is the Sequence of Returns Risk in its most dangerous form.
2. Scenario 2: 80% SPY / 20% Safety (Balanced)
Success Rate: The success rate is often found to be equal to or even slightly higher than the 100% stock portfolio, depending on the exact starting period analyzed. It sits in the 97% to 99% range.
The Benefit: The 20% safety buffer (short-term bonds, high-yield cash, etc.) acts as your Sequence of Returns shield. When the SP 500 crashes, you draw your annual cash flow from your 20% safe bucket, leaving your 80% stock allocation intact to recover. When the market recovers, you can rebalance by selling a little stock and topping up your bond/safety bucket.
The Trade-off: The final median portfolio value will be slightly lower than the 100% stock portfolio because 20% of your assets are invested in lower-growth assets. However, the difference in the success rate is the critical factor for a retiree.
???? Why the 80/20 Approach is Better for Most Retirees
The better approach in retirement isnt necessarily the one with the highest average return, but the one with the highest survival rate and the most manageable psychological risk.
1. Safety Margin (The Shield): The 20% safety allocation directly combats the Sequence of Returns Risk.
It provides cash flow for 4-5 years of expenses, allowing you to ride out a major recession without being forced to sell your stocks at a loss.
2. Behavioral Endurance: Can you truly watch your entire portfolio (100% SPY) drop by 40% and still confidently withdraw your annual cash? For most people, the stress would be immense, leading to panic selling or withdrawal cessation. The 80/20 split softens the volatility, making it easier to stick to the plan. Sticking to the plan is the #1 predictor of retirement success.
3. Inflation Defense: High-yield safety investments, particularly high-quality short-term corporate bonds or TIPS (Treasury Inflation-Protected Securities), can provide income that is less correlated with stock market volatility, offering a small hedge against unexpected inflation spikes that stocks might struggle with initially.
Final Verdict
In a long-term retirement scenario (30+ years) where you must draw down your assets, Scenario 2 (80% SPY / 20% Safety) is fundamentally superior because it provides a near-identical high success rate while dramatically reducing the one risk (Sequence of Returns Risk) that leads to catastrophic failure for the 100% stock portfolio.
