Proprietary databases

Most banks now have internal rating systems and maintain historic databases on default rates. Unfortunately at many banks this is a relatively recent phenomenon (recent in the sense that to be useful the data should cover at least one full economic cycle). Other problems are that definitions of ratings or their interpretation over time may change and there is often a lack of granularity in the internal ratings used. There also have to be questions over its usefulness as a reference point when such data covers a period largely characterized by a developing banking crisis, the crisis itself and its subsequent resolution.