Comparing the effectiveness of drugs is an important part of knowing how to best treat patients, yet little data about the comparative efficacy of new drugs is available at the time of their approval in the United States.  A study published in the Journal of the American Medical Association this year found that “[p]ublicly available FDA approval packages contain comparative efficacy data for about half of NMEs [new molecular entities] recently approved in the United States and for more than two-thirds of NMEs for which alternative treatment options exist.”  Seems to me that data for only half of new drugs approved in the US is not enough.  This article from Medical News Today further discusses the study.