I was surprised to read your Editorial “Brown's budget briefing” (Nature 440, 581; 2006), backing the UK government's recent suggestion that external research income should replace much of the current Research Assessment Exercise (RAE). An obvious problem with this proposal is that the RAE affects not only the funding of individual departments, but their hiring and firing policy too. Why would departments ever appoint postdoctoral researchers to junior lectureships if the RAE-replacement was a metric based on external research income? Whatever the quality of their research up to that point, postdocs only become eligible to be principal investigator on research council grants when in a permanent post. An already difficult career step for many postdocs would only get harder.