The yearbook recognises companies with best practices in sustainability in each sector at global level, and is published each year by RobecoSAM, a company specialised in Sustainable Investing.  

RobecoSAM's annual assessment of companies' sustainability is also used as the basis for selecting components of the Dow Jones Sustainability Index. The results of the 2014 assessment confirmed the inclusion of ACCIONA in the Dow Jones Sustainability World Index (DJSI World) for the eighth consecutive year, and this is the second year that the company has been evaluated as part of the 'Electric Utilities' sector as a result of the change in its business profile in recent years, which has resulted in greater exposure to renewable energy.

The Sustainability Yearbook 2015 includes the top 15% of companies in each sector in terms of social, environmental and corporate governance practices. A total of 1,995 companies worldwide in 59 sectors were evaluated this year.