One of my favorite Mr. Money Mustache articles is the “Shockingly Simple Math” post. It details how frugality is able to slash the time it takes to reach Financial Independence (FI). That’s because for every additional dollar we save we reduce the time to FI in two ways: 1) we grow the portfolio faster when we save more and 2) we reduce the savings target in retirement by consuming less.
That got me thinking: Is the math really that simple? How sensitive is the savings horizon to different rates of returns? What happens if we use historical returns instead of one specific expected return assumption? How important is the asset allocation (stock vs. bond weights) on the path to early retirement? How much does the equity valuation regime (e.g. the initial CAPE ratio when starting to save) matter?
So, in typical Big ERN fashion, I take an ostensibly simple problem and make it more complicated!
Let’s get the computer warmed up and start calculating…
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