How much scientific research is actually fraudulent?

How bad is the false-positive problem in scientific research? As I earlier reported, a 2015 editorial in The Lancet observed that "much of the scientific literature, perhaps half, may simply be untrue." A 2015 British Academy of Medical Sciences report suggested that the false discovery rate in some areas of biomedicine could be as high as 69 percent. In an email exchange with me, Ioannidis estimated that the nonreplication rates in biomedical observational and preclinical studies could be as high as 90 percent.

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...

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.