Sure, I’d bet that there has been, though at the scale of these numbers I suspect it might end up being lost in the large sample size similar to the cross-national inventors note. I think separating these out or not would also depend on what you are trying to get at with the data. For instance, I assume the point of this would be to allow us to count say an RCA (in the past) or other US company’s Taiwan branch as a “US” invention despite its first inventor most likely being noted as residing in Taiwan. This seems a bit counter productive, however, if the idea is to use patent counts to get an idea of where innovation is happening (there are a multitude of reasons a US company might set up an R&D or other patent producing entities in a foreign country, but at least one of those must be the idea that being there gives it an innovative advantage of some sort to balance out with other US-based centers).

Then again, if the goal is to talk about national/cultural innovativeness then using inventor locations has already been problematic for a very long time given the sheer number of foreign scientists and engineers who work in the United States (regardless of their immigration or, later, citizen status). An additional level of problem for this type of tracing based on company “nationality” is that it would require a fair amount of “touching” of each data point in a huge sample to follow not the assignee’s “country”, but its ultimate owner’s headquarter’s country. Many Taiwanese companies, for instance, use a corporate structure where the ultimate “owner” company is located in the British Virgin Islands (etc.). Should these count as Taiwanese or BVE (in my limited experience, patents tend to be held by the Taiwanese entity)? Where and how would we draw the line? In the Taiwanese case, while this “off shoring” has something to do with taxation issues, it often has more to do with skirting the strict investment restrictions that Taiwan’s ROC government puts on Taiwanese firms doing business in China (a BVE firm can easily own companies in both places, but a Taiwanese firm would have some difficulty owning a Chinese firm and vice versa).

Companies who stash a portion of their patent portfolios in patent holding companies (often with unrelated names) would also present some difficulty for tracing as I’m sure many in-house and in-firm folks have seen in their own patent threat searches.

As you noted in comment 3, then given Japanese (and Taiwanese) differences with US and European (or US or European?) patenting habits, to what degree can we use patent counts (or percentages of total issued in the US) as comparable indicators of anything? There is good reason to suspect, for instance, that while Chinese companies are innovating, that a large number of the patents being applied for in China are of somewhat questionable value.