The council taxbase projections used in the local government finance settlements for 2008-09, 2009-10 and 2010-11 are based on the billing authority’s taxbase as at 8 October 2007 adjusted for student exemptions, increased by the average annual increase between 2005 and 2007. The following link provides a detailed explanation:
http://www.local.communities.gov.uk/finance/0809/taxbase.pdf