How much research is fraudulent?

Fraudulent research has become an active topic over the past couple of decades. That interest notably gave rise to a “MacArthur Genius Grant” to establish the excellent website Retraction Watch. Now the issue has been taken up in Reason magazine. The topic is sure to spark controversy.
How Much Scientific Research Is Actually Fraudulent?
Ronald Bailey, Reason

". . . The possibility that fraud may well be responsible for a significant proportion of the false positives reported in the scientific literature is suggested by a couple of new Dutch studies. Both studies are preprints that report the results of surveys of thousands of scientists in the Netherlands aiming to probe the prevalence of questionable research practices and scientific misconduct.

Summarizing their results, an article in Science notes, “More than half of Dutch scientists regularly engage in questionable research practices, such as hiding flaws in their research design or selectively citing literature. And one in 12 [8 percent] admitted to committing a more serious form of research misconduct within the past 3 years: the fabrication or falsification of research results.” Daniele Fanelli, a research ethicist at the London School of Economics, tells Science that 51 percent of researchers admitting to questionable research practices “could still be an underestimate.”

In June, a meta-analysis of prior studies on questionable research practices and misconduct published in the journal Science and Engineering Ethics reported that more than 15 percent of researchers had witnessed others who had committed at least one instance of research misconduct (falsification, fabrication, plagiarism), while nearly 40 percent were aware of others who had engaged in at least one questionable research practice. . . ."