Understanding Society User Support

I would like to know, as far as possible, the attrition rate of the Understanding Society panel. Ideally, it would be useful if this was available on a wave by wave basis, and could also be broken down by sample: the main sample, the Ethnic Minority Booster sample, and the youth panel. Finally, if there is any information on how the attrition rate varies by region that would also be useful. Are there are any working papers or reports available that could provide this information? Thank you