Portfolio optimization for sustainable investments

Investments in firms related to environment, social responsibility and corporate governance (ESG) aspects have recently grown, attracting interest from both academic research and investment fund practice. This paper develops a simple new portfolio optimization approach to include ESG in portfolio formation. In addition to technical and practical advantages over a traditional mean--variance approach that incorporates ESG preferences, our approach allows us to follow competing explanations of the relation among risk, return and ESG. An extension of our portfolio optimization approach can even help distinguish competing explanations from the literature, i.e., between the preferences of investors for ESG firm characteristics and exposure to a common ESG risk factor. The proposed portfolio optimization approach is flexible enough to include additional risk factors and/or characteristics. We demonstrate the application of our approach to empirical data.