Fig. 1From: Trial registration and selective outcome reporting in 585 clinical trials investigating drugs for prevention of postoperative nausea and vomitingAnnual numbers of publications of all included trials (n = 585) from 1965 to 2017 (a) and of all registered trials (n = 75) from 2004 to 2017 (b). The first registered trial was published in 2004Back to article page