This would be great, except that it works algorithmically, not linearly. Check out this math:
- SPF 15 weeds out 93% of UVB rays
- SPF 30 catches 97%
- SPF 50 filters 98% of UVB radiation
As you can see, despite going up 20 digits in your SPF, you only get a 1% point increase in UVB protection, not a 20-point increase in protection.
Would this negligible amount be helpful for those with fair skin that burns easily? Maybe! But when you're buying that super-high SPF protection, know that it's not buying you much in added protection. In fact, the FDA wants the highest allowable SPF to be 50+, since that SPF 85 sunscreen is essentially selling you a false promise.
The other issue with spending more for higher SPFs is that these numbers aren't always accurate, especially if you're jumping in a pool regularly, or sweating, or not putting on enough. So you don't always need the highest SPF in town, and you can’t always trust the bottles, or your own ability to apply correctly.