I already mentioned that when I project out our portfolio growth I’m assuming a non-inflation adjusted rate of return of 8%. If inflation were to average 2%, then my real return would actually be just 6%. I could just assume a lower rate of return, but I prefer to make some more granular assumptions about inflation.
It All Starts with Budgeting
Each year, I pull our full years' expenses by category and make some minor adjustments to come up with a representative retirement budget.
First, I eliminate principal and interest payments on our house. Our mortgage will be paid off well in advance of retirement, so this won’t be needed. Next, I reduce our income taxes to account for lower income in retirement. I also reduce our charitable giving amount to account for us not having an income to tithe from, but not to zero since we will still want to be generous in retirement. Lastly, I eliminate any retirement account contributions since I won’t be eligible to contribute.
Not all of our expenses will be lower in retirement. I adjust our healthcare and travel expenses by assuming they will each be double current levels. Everything else stays the same. After all of these adjustments, I’m left with a budget that is roughly half of our household expenses. That sounds really low, but the majority of our current expenses are paying down the house, income taxes, and charitable giving so it is not unrealistic. In some categories like groceries, it may even be high given that we currently cover food for a family of six and will someday be empty nesters.
With this representative budget, I then apply inflation assumptions. The key difference here is that I use different inflation assumptions for different categories. Historical inflation has been 3-4% and I assume for most categories an inflation rate of 3%. The average for my lifespan hasn't exceeded 3%, but it's a real risk that it could be much higher. For me, medical expenses are the big wildcard. Not only do I assume they will be double my current level of spending, I also assume an inflation rate of 7% on medical expenses. If I were budgeting to be paying for higher education costs in retirement (I’m not), I would use a 7% inflation assumption for those costs as well.
Using this representative budget and specific inflation rates, I then inflate our expenses by the number of years between now and retirement to get an inflation adjusted retirement budget. Each year of retirement, I assume that expenses will continue to increase at the rates outlined above.
Inflation Impact on Retirement Income
One very interesting thing to consider is how inflation can eat away at your portfolio. For simple numbers, let’s assume you retire and have $1M worth of investments to live off of. It's an oversimplification, but let's also assume a steady 8% return, 3.5% inflation, and first-year expenses of $60,000. Since $60,000 is 6% of $1,000,000 and you’re earning 8%, then you can live off the earnings forever, right? Wrong.
You see, what happens is that even though you are consistently earning 8%, the growth of your earnings is lower than that because you aren't reinvesting all of those earnings. Because your expenses are growing at 3.5%, and your income isn’t growing as quickly, your expenses will actually be greater than your income after just 15 years. After that, you begin whittling away your principal until year 33 when you run out of money entirely.
In this way, inflation is one of the biggest risks to early retirement. Everyone is impacted by inflation. The longer your retirement, the more time inflation has to grow and exceed your investment income.
Below I've outlined what hypothetical portfolio values would be with the assumptions outlined earlier.
How to protect against inflation?
There are a few things I am doing to protect our retirement dreams from inflation. The first is to have an initial withdrawal rate much lower than 6%. In your working years, you want to have as big a gap as possible between income and expenses. In retirement, you want to have a gap between expected investment income and expenses. Whether you plan to spend most of your money in your lifetime or leave an inheritance, inflation can derail either of those plans.
The primary other strategy is to remain invested in stocks. Over time, stocks are the only asset class that has consistently outperformed inflation. While earnings growth may not exceed inflation, left untouched a diversified stock portfolio would not lose purchasing power over time.
There are many ways to account for inflation in retirement planning, but this simple method works for me for now. It is absolutely something you don't want to ignore, but I don't lose sleep over it either. What are your inflation assumptions?