What Happened
When a product infringes a patent, damages should reflect the value of the patented invention—not the value of everything else in the product. This is "apportionment." If your patent covers one feature of a smartphone, you shouldn't get damages based on the entire phone's value unless that feature drives demand for the whole thing.
Why It Matters
This sounds reasonable, but it's one of the biggest fights in patent damages. Patent owners want to calculate royalties on the entire product—that's a bigger number. Accused infringers want to calculate based on the smallest component that practices the patent—that's smaller.
The "entire market value rule" says you can use the whole product as the damages base only if the patented feature drives demand for the entire product. Otherwise, you need to use the "smallest salable patent practicing unit"—the smallest component that can be sold separately and practices the patent.
For complex products like smartphones, servers, or cars, this matters enormously. A patent on one software feature could mean damages based on a $5 chip or a $1,000 phone. That's a 200x difference.
What You Should Know
If you're enforcing patents, think carefully about your damages theory. If you can show the patented feature drives demand for the whole product, go for it. If not, be prepared to apportion. Hire a qualified damages expert who understands the rules.
If you're defending, challenge the damages base. Push for apportionment. Question whether the patent really drives demand for the entire product. Attack the expert's methodology.
Apportionment prevents patent owners from capturing value they didn't create. It's a fundamental principle that keeps damages tied to actual invention value.