Trucost, with its comprehensive data on corporate environmental impacts, is a key partner to Newsweek in helping unlock the most significant problem in creating a definitive environmental scorecard: there is a lack of corporate reporting of even the most basic environmental data. Trucost's comprehensive approach allows it to evaluate the environmental impacts of a company whether a company reports its emissions or not, and even when the company itself does not know what its impacts are.

In creating the first ever definitive environmental scorecard for the biggest companies in the U.S., Newsweek has taken on a challenging task. Let’s understand the problem. Overall, only 188 companies of the 500 analyzed adequately disclose data on their greenhouse gas emissions. Of those, 69 of the top 100 disclose compared with only 29 of the bottom 100. Emissions of other polluting gases, water use and solid wastes, are reported even less.

Where reported data is available, there is still a need for standardization as not all companies use the same protocol, or agree on what should be measured. Most figures are self-reported and not independently checked by a third party. Trucost reviews reported data and puts it in a standardized and comparable form to allow for comparisons of environmental impacts across businesses.

The 500 companies included in the ranking were chosen by revenue, their market capitalization and number of employees.

To generate a meaningful ranking in a framework of poor disclosure, Newsweek collaborated with three expert, independent research partners on this first-ever environmental ranking of major U.S. companies:

• Trucost, which has created the world’s most comprehensive quantitative data on corporate environmental impacts
• KLD Research & Analytics, which tracks environmental, social and governance information on companies worldwide
• Corporate Register.com, the world’s largest online directory of company-issued social responsibility, sustainability and environmental reporting.

The goal was to assess each company's resource use and emissions, environmental policies and strategies, and reputation among its peers.

Each of the three Newsweek partners scored the companies in the Green Rankings according to their own methodologies, and then converted their results to Z-scores, a statistical technique that measures how well a firm compares to the average score of the collective group. The overall Newsweek Green Score was calculated as the weighted sum of the three component Z-scores: 45% for environmental impact, 45% for green policies, and 10% for the reputation score.

Newsweek's methodology and weightings were created in consultation with its three partners on the project, and an independent advisory panel.