Index of Environmental Indicators

The indicators in this report show improvements in many areas that are of environmental concern including the quality of air and water, the use of natural resources, and the management of solid wastes. This section develops an index that measures improvements or reductions in overall environmental quality for the United States and Canada. The index shows that the relative severity of environmental problems is decreasing and that environmental quality in most categories is improving relative to the quality in 1980. It also shows that, both in the United States and in Canada, overall environmental quality has improved relative to 1980 levels.

Methodology

To aggregate individual environmental indicators such as lead, phosphorus, and soil erosion into a single measure of environmental quality, a common unit of measure is required. To create the index of environmental indicators, annual values within each of the four main categories (air quality, water quality, natural resources, and solid waste) are converted to the base year 1980. This makes it possible to compare environmental quality in later years to the base year. It is important to note that this approach allows a comparison of relative values only. The base-80 values do not provide any information about the absolute level of environmental quality. This is unavoidable as assessments of absolute environmental quality are value judgments, beliefs about the ``state of nature'' that are social constructs varying among societies and over time.

Base-80 values are comparable across categories because they are measured in the same units. For the same reason, these values can be averaged. A second technical issue arises when determining the weight assigned to each indicator. For example, it is difficult to quantify the respective weights to be given to air pollution and water pollution. For this reason, no attempt is made to give relative weights to each indicator. For each year, base-80 values are averaged within each of the four environmental categories (air quality, water quality, natural resources, and solid waste). The category averages are then weighted equally to arrive at an overall average for each year. The resulting time series represents the general trend in environmental quality for the United States and Canada.

It was necessary to account for missing data in many categories because the available time-series environmental data are often incomplete. Straightforward linear regression techniques are used to estimate missing values. In cases where trends are improving, however, the law of diminishing marginal returns may begin to have a significant effect. This means that future improvements may be more difficult to achieve than past ones. In such cases, linear projections would overestimate the rate of environmental improvement. For this reason, linear projections are used only to interpolate, that is, to fill gaps between known data points and years without data. Forward projections are conservatively estimated: they use the last known data point as an estimator for later years with missing data. This technique ensures that no additional environmental improvement is assumed where data are missing. In cases where backward projections are necessary, missing data are also conservatively estimated. As a result, the index of environmental indicators likely underestimates the actual improvement in environmental quality relative to 1980.

Results

Tables 15 and 16 show the base-80 values for each environmental indicator as well as category and overall averages for the United States and Canada from 1980 to 1995. The category averages are presented graphically in figures 51 and 52. The trend in each country is clear: relative to the situation in 1980, environmental pollution is declining in severity in the categories of air quality, water quality, natural resources, and solid waste. On average, overall environmental problems in the United States in these categories were 19.2 percent less severe in 1995 than in 1980, and 13 percent less severe in Canada (figure 53).

The greatest improvements in the environment in both countries were in air quality and water quality. In Canada, overall ambient air quality improved by 39.3 percent while water quality improved by 27.1 percent between 1980 and 1995. During the same period, American ambient air quality showed an 44.4 percent improvement, while water quality improved by 36.8 percent. The improvement in water quality, however, should be taken with a note of caution as the available data represent only a small fraction of the number of rivers, lakes and streams in each country.

While these trends are encouraging, a few indicators showed a decrease in environmental quality. For example, ground-level ozone levels deteriorated in Canada in the 1980s. Because ground-level ozone is the result of many factors, its reduction remains a particularly difficult regulatory problem. In addition, freshwater consumption in Canada increased relative to renewable freshwater resources. However, since Canada has abundant water resources and since freshwater consumption could be drastically reduced by allowing it to be sold at market value, this trend may not be of great concern.

In the United States and Canada, municipal waste generation has increased substantially since 1980; recycling rates, however, have increased as well. While Americans and Canadians produced increasing amounts of refuse, fewer economically valuable resources were being sent to landfills and incinerators. In addition, using the total amount of waste generated as an indicator of environmental quality may overstate the waste problem, as there is no shortage of landfill space in either the United States or Canada.

Conclusion

The index of environmental indicators for Canada and the United States shows that fears about increasing environmental degradation in Canada and the United States are unfounded. In both countries, environmental quality is getting better, not worse. While it is impossible to determine the exact magnitude of the improvement in the environment due to the difficulty in determining how overall environmental quality should be measured as well as the lack of data for some important categories, the direction of the change in quality is clear. While there are still some serious environmental problems that need to be addressed, the overall trend in environmental quality continues to improve.

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Last Modified: Wednesday, October 20, 1999.