It’s time for a new post in the Safe Withdrawal Rate Series. It’s been a while, I know! This is a post I’ve been mulling over for a long time and a recent suggestion from a reader made me revisit my notes again. Why not calculate sustainable withdrawal based on how accountants or actuaries work. No simulations necessary! Neither historical nor Monte Carlo simulations! And here’s the kicker: you run this SWR calculation with all the data you’re going to assemble to use my Google SWR Sheet already. No extra work necessary! So, what do we have to do? Very simple:
- Take stock of all of your asset and liabilities today
- Take stock of all of your future expected cash flows: both positive (Social Security, Pensions, etc.) and negative (health expenses, kids’ college expenses, etc.).
This is essentially the information that you’d already need to know when doing a Safe Withdrawal Rate analysis, specifically, the inputs for the Safe Withdrawal Google Sheet, see Part 28 of this series!
So, how do you calculate a safe withdrawal rate without simulating anything? Very simple, use Net Present Value (NPV) calculations to transform all future cash flows (Social Security, Pensions, annuities, etc.) into today’s values, so you will end up with an adjusted net worth that takes into account not just your current assets and liabilities but also all of the future flows. And again, those future flows can be positive (Social Security, pensions) or negative (setting aside money for health expenses, nursing homes, etc.)
Once we have this “adjusted net worth” we can simply do a “reverse NPV calculation” to determine what retirement budget will exactly match our net worth. And that’s a sustainable retirement budget the way an actuary or an accountant would likely compute it.
Before everybody gets too excited, though, let me state the obvious: I would not recommend relying exclusively on this one approach and you’ll need to rely on simulations after all – more on the disadvantages below. But I certainly like the simplicity and some of the information we can gather from this approach!