The thread is "the diminishing impact of modern paper because ... " with the alternative suggestions that a) 'every scientists know they are not worthy', and b) 'because they are behind a paywall'.

You replied to (b), saying that that likely wasn't the case because "I can't see paywalls being an issue. It certainly never was for me or my former colleagues [at academic institutions]."

My reply is two-fold. First, it affects me. I am writing a paper. I have excellent citations from the 1950s to 1980s because all of that is on paper, which is easily ("cheaply") accessible to me. I don't have good citations for the 1990s and onwards because those cost something like $30 each from the publisher. (It's actually cheaper to get most of them through Interlibrary Loan, which has much lower page charges than the publisher.)

Hence, just like you have observations that it doesn't affect your research, I have a counter-observation that it does affect my research.

The second point was to highlight your implicit suggestion that nearly all research is done at academic institutions. While you didn't say it explicitly, your counter-argument is very weak unless you make that assumption. I don't think you meant to make a weak argument. With the same weak argument, I could say that it affects me, and friends of mine who are self-employed or working in small companies, so therefore everyone must be affected by it.

Now, I think it's true that most published research is from academics, though since I work in mostly pharmaceutical chemistry I can say that many publications in my field come from industrial research.

"If you want to publish you can't submit a paper for review without having demonstrated knowledge of the related literature, and where your work fits within that."

Yes, I know that. The cost of doing the literature research has made it very hard for me to publish. Indeed, that's my point. As a self-funded researcher, I can say that science is an expensive endeavor.

"and thus can't be used an excuse for lower citations for more recent papers"

Strictly speaking that's not true. It could be that more people are publishing historical reviews. It could be the modern trend to include older citations. If you look at papers from the 1950s, you'll see that there might only be a few citations. By comparison, the modern citations sometimes seem to use the citations as a badge of honor, or proof that the person is scholarly.

Based on the evidence in the paper, therefore, you cannot make the conclusion you did. Nor can the paper's authors, since all the paper did was observe a trend that is in alignment with the hypothesis. The next set of tests might be to pick out a selection of papers and ask people now to judge which items need a citation. If the same set of judges say that papers from the 1990s should have had more citations, then this would suggest that there's been a cultural change.

The paper suggests that multiple factors may be involved. It does not identify which of those are the most important. They point out that the chemistry field is one of the few which hasn't changed. This happens to be my area of experience.

Mechanical search of chemical documentation started in the 1940s with punch card machines. Organizations like CAS, from the American Chemical Society, have long existed to make chemical documentation more searchable. Companies like ISI (now Thompson Reuters) started in the 1960s to computerize entry and keyword-based search, with online searches by the 1980s, though not full-text search.

The lack of change may indicate that the search technology of the 1980s, based on human indexing and keyword searches, is sufficient for the gains seen. To be fair, chemical publications is more open to keyword indexing than, say, Health & Medical Sciences. (I know this from reading some of the ISI publications, dating from when they entered the Health & Medical Sciences field.)

This paper says "between 1990 and 2013, the number of scholarly articles published per year grew close to 3-fold. As a result, there is much more recent work for researchers to learn from, build upon and cite". I've been reading the chemical documentation literature from the 1960s and 1970s. They were talking about exponential growth back then.

For example, I have a chemical information text book from the early 1970s saying that the doubling time for chemical documentation is about 13 years. I checked the modern numbers, and it's still holds.

If the exponential rate of growth is the same then and now, then a paper in 1990 would be equally biased towards recent decade papers, on a percentage basis, as someone writing now. That's how exponential curves work.

So, I'm not all that convinced about the paper. They aren't able to distinguish between a cultural change and an access to information change, or if it's due to improved search technology (eg, 1970s tech but with auto-indexing) or due to easier access to the literature.