The policy costings for the changes to stamp duty land tax included behavioural analysis. Details of the behavioural effects considered are available in the published policy costing note (pages 21-23)"http://cdn.hm-treasury.gov.uk/budget2012_policy_costings.pdf"The policy costing was undertaken by HM Revenue and Customs. The policy costing and its underlying methodology were certified by the Office for Budget Responsibility as representing a reasonable and central view given the information currently available.