There is an old adage that cautions about the consequences “when you assume…”
And yet, the business of retirement planning is replete with any number of so-called “common wisdom” rules of thumb. Doubtless many have well-intentioned origins – to make complicated concepts easier to grasp, and thus to address.
One of the more pervasive notions is that a realistic target for retirement savings can be determined by accumulating a sum that will provide an income stream equal to a percentage of one’s pre-retirement earnings – a sum that is generally expressed as 70-80% of what you earn prior to retirement. This starting point - generally called
a "replacement ratio" - includes any number of imbedded assumptions, perhaps most significantly that the individual will need to spend less post-retirement, generally understood to be on things such as taxes, housing, and various work-related expenses (including saving for retirement).
Moreover, the replacement rate approach represents, at best, an indirect approach in evaluating whether retired workers can maintain their standard of living in retirement – because what matters is not how much you have to spend, but how much you need to spend. A recent research report sponsored by the Society of Actuaries’ Pension Section, “Moving Beyond the Limitations of Traditional Replacement Rates”, also highlights the limitations of relying on replacement rates. A recent paper published by the Center for Retirement Research at Boston College (“How Much to Save for a Secure Retirement”) acknowledges that “the most direct approach would be a comparison of household consumption while working with consumption after retirement” – before launching into a discussion that instead draws on a relatively simplistic series of assumptions , not the least of which is that the goal of retirement saving is a replacement rate of 80-percent of one’s pre-retirement income.
The problem is that these assumptions are just that – and, as a result, in some cases that 80% will be more than is required – and for some it will, unfortunately, be less. Furthermore, most of the assumptions underpinning such replacement ratio targets are implicitly using a 50 percent probability of success.
Additionally, these replacement rate models tend to ignore one – or more – of the most important retirement risks; investment risk, longevity risk, and risk of potentially catastrophic health care costs.
The reality is that there is no “correct” single replacement rate, but the factors that undermine those simplistic rules of thumb are quantifiable. Those factors, and the importance of probabilities in retirement planning are detailed in “Measuring Retirement Income Adequacy: Calculating Realistic Income Replacement Rates (EBRI Issue Brief No. 297).
After all, it isn’t what you have accumulated at retirement that matters, it’s how much you have left at the end of it.
- Nevin E. Adams, JD