This Sustainability Board led Task and Finish Group have supported HM Treasury’s ‘Green Book’ review by undertaking an actuarial review of the discount rate underpinning the Green Book’s assessment of transformational change. The Green Book is a key policy document which sets out the government’s guidance for appraising all publicly funded policies, programmes and projects. The group’s report highlighted challenges when applying the Green Book’s current methodology to transformational projects, which continues to leave them at risk of undervaluation. This is both due to technicalities in the Green Book discount rate guidance and an over reliance on numerical results, in the form of cost benefit analysis, when appraising projects. Recommendations made to HM Treasury include a request to update the historic analysis which underpins both individual discount rate components and the overall rate’s declining schedule to allow for up to date estimates of future growth and increased uncertainty due to climate change.   

Co-chairs: Sara Joslin and Wendy Walford

Established: 2025