Patent Law FAQ

A result-effective variable is a parameter that is recognized in the prior art as affecting a particular result or outcome. The concept is important in patent law, particularly in obviousness determinations. According to MPEP 2144.05:

“A recognition in the prior art that a property is affected by the variable is sufficient to find the variable result-effective.”

The idea behind the result-effective variable analysis is that a person of ordinary skill would be motivated to optimize a parameter if there is evidence in the prior art that the parameter affects the result. However, it’s important to note that after the KSR decision:

“[T]he presence of a known result-effective variable would be one, but not the only, motivation for a person of ordinary skill in the art to experiment to reach another workable product or process.”

Applicants can rebut a prima facie case of obviousness by showing that the claimed variable was not recognized as result-effective in the prior art, but this is considered a narrow exception.

To learn more:

• result-effective variable
• patent law
• obviousness
• optimization
• KSR