The following outlines the first phase of work on material flows reported in the 1997 WRI report Resource Flows: The material basis of industrialized economies. Prepared by WRI and colleagues in Germany, Japan, and the Netherlands, the report proposes preliminary indicators on materials inputs to economies and points to some of their implications.

1. The Total Materials Requirement indicator is the physical materials used by a national economy -- the sum of domestic and imported primary natural resources and their hidden flows. The per person requirement appears to be leveling off at about 75 to 85 metric tons per year in Germany, the Netherlands, and the United States. Japan’s requirement is about 45 metric tons.

2. Hidden flows matter. Overburden from mining, earth moving for construction, and soil erosion are often not considered in environmental analyses because they are not priced. However, they account for almost three-quarters of U.S. flows and are a major source of run-off, habitat loss, and other types of ecological damage.

3. Fossil fuel use is overwhelmingly the largest contributor to the Total Materials Requirement in Germany, the Netherlands, and the United States and second in Japan.

4. Policies matter. U.S. agricultural flows decreased as the Conservation Reserve Program paid farmers not to farm highly erodible lands and infrastructure flows shrank as the federal interstate highway system was completed. Private construction is a growing source of U.S. flows related to infrastructure construction. Material flows information may point to the need for new policies.

5. To the extent that environmental damage from hidden flows is not included in the prices of commodities, the countries that benefit from using the natural resources are not the same as those paying the ecological costs of using them. For smaller countries, the proportion of the Total Materials Requirement that occurs outside the country and is usually not included in prices ranges from 35 to 70 percent. The United States is more self-sufficient but important extractive flows (such as oil and bauxite and their environmental impacts) occur in other countries to support use of the materials in the United States.

6. The materials intensity of economies can be calculated by comparing the Total Materials Requirement with the Gross Domestic Product (GDP). The environment ministers of the 29 members of the Organisation for Economic Cooperation and Development agreed in April 1998 "to promote innovative approaches, such as eco-efficiency, aiming to achieve substantial improvements in resource productivity, for example by a factor of 4 and eventually of 10." To generate $100 of income in Germany, the Netherlands, or the United States now requires about 300 kilograms of natural resources, including hidden flows. A fourfold reduction translates into an intensity of 75 kilograms per $100 of GDP. The Carnoules Declaration, issued by a group of environment and development leaders, calls for cutting global non-renewable material flows by half over 30 to 50 years. To do this, they suggest reducing material intensity in industrialized countries by tenfold -- to 30 kilograms.