However, around 10 per cent of the papers were retracted, implying something more nefarious was going on.

From Science Fictions by Stuart Ritchie.  Page 60.

 The stories of Hwang and Obokata are both unusual in one obvious respect: the extraordinary prominence of the fraudulent papers. These were publications in Science and in Nature, two of the world’s leading journals. That such conspicuous fakes made it through these journals’ vetting process is concerning enough, but their prestige meant that the papers immediately captured the world’s attention – and its scrutiny. If this kind of fraud occurs at the very highest levels of science, it suggests that there’s much more of it that flies under the radar, in less well-known journals. Which raises the question: how often do biologists fake the images in their papers? In 2016, the microbiologist Elisabeth Bik and her colleagues decided to find out.

They searched forty biology journals for papers that included western blots, eventually finding 20,621.  In a genuinely heroic set of analyses, Bik personally looked through every single one and checked for inappropriate duplication in its photographic images. What she found was enough to populate a gallery of dodgy scientific pictures several times over: not just basic duplications (see Figure 1, below, for an example), but duplications with Hwang-esque cropping, Obokata-esque splicing and resizing, and a whole host of other dishonest techniques. In all, 3.8 per cent of the published papers (around one in twenty-five) included a problematic image. In a later analysis of papers from just one cell-biology journal, Bik and her colleagues found an even higher percentage: 6.1 per cent.  ] Of these, many were just honest mistakes and the authors could issue a correction that solved the problem. However, around 10 per cent of the papers were retracted, implying something more nefarious was going on. If those numbers are representative of cell biology papers in general, Bik calculated that there are up to 35,000 papers in the literature that need to be retracted. There was at least some positive news: more prestigious journals appeared on average less likely to have published papers with image duplication. Perhaps most intriguing, though, were the results about repeat offenders: when Bik and her team found a paper with faked images, they checked to see if other publications by the same author also had image duplications. This was true just under 40 per cent of the time. Duplicating one image may be regarded as carelessness; duplicating two looks like fraud.

Not a lot of perpetrators but with the capacity to taint the whole pool.