Environmental, social, and corporate governance (ESG) issues are often referred to by investors as “nonfinancial information.” As Robert G. Eccles, a professor of management practice at Harvard Business School points out, that’s not because these issues don’t have financial consequences. Rather, it’s because there are no standards for how to measure and report on ESG issues, unlike a company’s financials. Eccles, a mathematician by training and one of the foremost experts in corporate reporting, has for the past five years been working to create sustainability accounting standards for the investment community (he is also the chairman of ESG asset management firm Arabesque Partners). It’s been slow going. As world leaders gathered in Paris for the 2015 United Nations Climate Change Conference, I spoke with Eccles about the effort to provide nonfinancial information with the same level of accounting rigor as traditional reports—and what that would mean for the global effort to build a sustainable economy.