A portfolio constructed with a green overlay would emphasize bonds that are issued to finance green enterprises or infrastructure; issuers commonly define the uses for which proceeds may be used, and some larger issues obtain third-party certification of green character. Most green bonds issued to date are rated based on the overall credit quality of the issuer. There is limited history on which to form a judgment, but to date we have seen no evidence of investing in green bonds reducing return or increasing risk. We use the term “green overlay,” because the green bond market is in its early stages, and it may not be possible or appropriate to populate an entire portfolio with green bonds. To the extent that access to green bonds is limited, we intend to fill out such portfolios with bonds that do not ostensibly finance harmful enterprises or projects.