In the most recent ERA (2015) there was a new outcome produced for just a few fields of research in a few universities: "not ranked". While fewer than 1.5% of submissions were not ranked, these few outcomes surprised both the universities and the public, and generated substantial public debate. The debate focused on practices of gaming or ‘coding errors’ within university submissions as the reason for this outcome, laying the blame for the outcomes at the door of the universities and the submissions they made to the ERA process.
In a recent paper, Paul Henman (from UQ), Scott Brown, and Simon Dennis argue that the universities' submissions were only part of the explanation. With the support of statistical modelling, they showed that unrated outcomes are more likely to have arisen from particular practices within the ERA's ranking committees; particularly the committee which ranked the discipline of Psychology.
The full paper is available here: