Sustainability indexes: why join in? A study of the ‘Corporate Sustainability Index (ISE)’ in Brazil

In the past decade, indicators have been created to assess the sustainability performance of companies listed in stock exchange markets. Academics and practitioners expect companies to benefit from being listed in such indexes, but evidence of value creation is still scarce. Since virtually all studies about the Corporate Sustainability Index (ISE) of the São Paulo Stock Exchange (Brazil) – the object of the present study – focused on the value of shares, we initially looked for answers in the finance theory. We collected secondary data about the financial and economic performance of companies forming the ISE's ‘theoretical portfolio’, as these kinds of indexes are also known. In a second stage, we sought additional motivations for companies to make efforts to be listed in the index. We collected additional data and interviewed representatives of key companies listed in the ISE, as well as industry leaders who chose not to participate in the selection process. The results support the main propositions of the institutional theory, as well as the ‘pays to be green’ literature – that the intangible value created by voluntary environmental initiatives, such as access to knowledge, new capabilities and reputational gain, better explain the efforts companies make to be listed in the ISE index.