Not often NEJM knocks it out of the ballpark compared to BMJ, but sure did here: 364 trials in 2016 in the big 5 med journals. BMJ had protocols for 50%, NEJM & JAMA >95%. Statistical analysis plans: <10% BMJ/Lancet, 92% NEJM HT
Availability of study protocols for randomized trials published in high-impact medical journals: A cross-sectional analysis