It is known that statistically significant results are more likely to be published than results that are not statistically significant. However, it is unclear whether negative results are disappearing from papers, and whether there exists a 'hierarchy of sciences' with the social sciences publishing more positive results than the physical sciences. Using Scopus, we conducted a search in the abstracts of papers published between 1990 and 2014, and calculated the percentage of papers reporting

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... ginally positive results (i.e., p-values between 0.040 and 0.049) versus the percentage of papers reporting marginally negative results (i.e., p-values between 0.051 and 0.060). The results indicate that negative results are not disappearing, but have actually become 4.3 times more prevalent since 1990. Positive results, on the other hand, have become 13.9 times more prevalent since 1990. We found no consistent support for a 'hierarchy of sciences'. However, we did find large differences in reporting practices between disciplines, with the reporting of p-values being 60.6 times more frequent in the biological sciences than in the physical sciences. We argue that the observed longitudinal trends may be caused by negative factors, such as an increase of questionable research practices, but also by positive factors, such as an increasingly quantitative research focus.