Do drug companies and other commercial entities have an obligation to report the results of the clinical trials they have sponsored? Interesting question, that. Most trials for novel therapeutics and diagnostics are paid for almost entirely by the sponsors, but knowing trial results would almost certainly present opportunities for new healthcare advancements.
Another interesting question: what percentage of clinical trials are actually reported? "Easy" to resolve. We know that all clinical trials are required to be registered ( U.S. by law, foreign by journal publication obligation). So our set of known trials seems
pretty solid. Then it's "just" a matter of linking all available papers to all trials with redults.