MHCLG/DLUHC Additionality Guidance

Pion Economics has been working, during the COVID 19 period, alongside AMION Consulting, Mott MacDonald and Thomas Lister, to undertake research into the additional impacts (or additionality) of housing supply interventions.

The research has combined both top down (econometric modelling) and bottom up (case study) approaches to assess completed supply-side housing projects supported by Homes England or its predecessors (the Homes and Communities Agency and English Partnerships).

Pion Economics has been responsible for the econometrics element of the study, undertaking quasi-experimental, pooled-cross-section hedonic price model (HPM) modelling in which post-intervention trends in house prices are assessed across distance-based rings proximate to the intervention and relative to a ‘control’ ring beyond which any displacement impact is not anticipated to occur.

The study uses Land Registry, property price data as the basis of the analysis.  It applies a dimension reduction approach to reflect the role played by amenity variables in determining price and applies spatial filters to accommodate spatial dependence.