The research they cited just says that older people tend to file more patents. This is just one component of innovation.
Guess what most twenty year old don't have?
[0] https://www.vox.com/2015/3/16/8225165/patents-innovation-soc...
Patents are typically filed by folks working for large(ish) corporations or universities. For corporations its almost a given that someone senior up the chain is on the patent. In a university - its generally the professor(s) leading the lab that will always be on a patent filed on behalf of the lab irrespective of the work they've put into it. That behavior in itself is a bias towards having an older population be on more patents.
> For corporations its almost a given that someone senior up the chain is on the patent.
In my experience that isn't true and in cases where it did happen it would be an abuse of process. As a rule, royalties from patents are assigned to the employer, so there's very little to be gained by being an inventor that's tangible. All I and my co-inventors got were a few low denomination US and Canadian bank notes.
At my employer that's the case . Directors are pretty much on every patent that comes from their department.
Inventors' dates of birth aren't on patent applications. To carry out the research, the authors of http://www2.itif.org/2016-demographics-of-innovation.pdf had to contact the inventors directly, so would have been able to filter out obvious cases of abuse.
So they come up with "studies suggest" and other nonsense like it.
Wasn't there an article a while back about how you lose your creativity and innovative powers as you grow older. And that's why most "innovation" in math, physics, tech and music come from younger people?