Delta Attribution: A New Method for Understanding Changes in Portfolio Emissions

As organizations gain more experience in measuring the financed emissions of their investments and loans, they often find that the year-over-year changes in emissions are not what they were expecting. Financed emissions depend on factors beyond just the actions of the portfolio managers or the companies that they finance. An attribution model is used to attribute the changes in emission to the different factors causing the change. It is therefore a powerful tool for understanding, explaining, and managing portfolio emissions. Attribution models have two main components: the mathematical method for calculating the attribution and the choice of explaining factors. This article compares several different methods and alternative choices of factors. The proposed model uses a method and factors that are widely used in other applications in portfolio management and sustainable finance—however, their application to this problem is new. Consequently, the attribution results are familiar and intuitive to financial professionals. The new model is then applied to a multiyear global equity portfolio example.