The Dangerous Allure of 'Average'
When planning for retirement, it is tempting to plug in a long-term average for stock market returns—say, 10%—and a historical average for inflation, perhaps 6%. These numbers feel concrete and reassuring. However, you don't live in an 'average' year;
you live through real-world volatility. The order, or sequence, in which you experience returns has a massive impact. A few years of poor market performance at the beginning of your retirement, when you start withdrawing money, can be devastating. Selling assets in a down market to cover expenses means you lock in losses, leaving a much smaller portfolio to benefit from an eventual recovery. This is known as the 'sequence of returns risk', and it is one of the biggest threats to a secure retirement. Two people with the same starting corpus and the same average return over 25 years can have wildly different outcomes, simply based on when the bad years occurred.
Inflation: More Than Just One Number
Just as market returns are not linear, inflation does not move in a straight line. Using a single long-term average ignores the reality of inflation spikes and the different ways costs increase. For instance, healthcare inflation often outpaces the general consumer price index, which is a critical factor for retirees. A period of high inflation early in retirement can permanently reset your cost of living to a higher base, forcing you to withdraw more money than planned for the rest of your life. To build a robust plan, you must test for different inflation scenarios: a baseline using historical averages, a higher-than-expected scenario reflecting recent spikes, and even a low-inflation environment that might affect the returns on certain assets. Modelling for a severe, 6% inflation scenario, for example, ensures your plan is prepared for fluctuations that could seriously reduce your savings' purchasing power.
How to Stress-Test Your Financial Future
So, how do you move beyond simple averages? The answer is stress-testing. This involves creating multiple 'what-if' scenarios to see how your portfolio holds up under pressure. You can start simply by modelling a 'best case' (high returns, low inflation), a 'worst case' (a market crash early in retirement, high inflation), and a 'moderate' case. A more sophisticated method used by financial professionals is the Monte Carlo simulation. This technique runs thousands of possible scenarios by randomly combining different sequences of returns and inflation rates based on historical data. The result isn't a single number but a probability of success—for example, an 85% chance that your money will last throughout your retirement. This shows how likely your strategy is to succeed under various market conditions, giving you a much more realistic picture of your financial health.
Building an All-Weather Retirement Plan
The goal of stress-testing isn't to predict the future—which is impossible—but to build a resilient plan that can withstand a wide range of outcomes. If your plan shows a low probability of success in a Monte Carlo simulation, it’s a sign that adjustments are needed. These adjustments are your levers of control. You might consider increasing your savings rate, delaying retirement by a few years, reducing your planned withdrawal rate, or adjusting your asset allocation. For example, shifting to a more conservative mix of 60% stocks and 40% bonds can help minimise risk as you approach retirement. Another effective strategy is creating 'buckets' for your money: a short-term bucket with cash and conservative investments for immediate expenses, and long-term buckets that remain invested for growth. This prevents you from being forced to sell growth assets during a market downturn.
