In high cost-of-living cities, rent and essential expenses alone can easily exceed 50% of income for many earners, especially early in their careers, making the framework feel aspirational rather than practical at that life stage. Conversely, someone with a paid-off home in a lower cost-of-living city might comfortably save well above 20% without much sacrifice.
Rather than treating the exact percentages as a rule to force yourself into, it's more useful as a diagnostic: if your "needs" category is consistently eating 70-80% of your income, that's a signal worth examining, whether through re-evaluating fixed costs like rent or, over time, through income growth.
The 20% savings figure is worth protecting as a floor rather than a ceiling wherever possible — even if needs and wants don't split neatly into 50-30, prioritising a minimum savings rate before it gets absorbed into lifestyle spending is the part of this rule most worth keeping.