Because the decentralised agencies were set up on a case-by-case basis over the years, to respond to emerging individual policy needs, they have been operating in quite diverse conditions. In 2012 the EU rectified this by adopting a comprehensive set of guiding principles – a "common approach" – to make the agencies more
coherent, effective and accountable.
This new framework was the result of analysis by an EU working group of the agencies'
governance, functioning and oversight, based on a number of reports and studies, including a comprehensive external evaluation.