Another possibility is computing total environmental costs as a percentage of sales and tracking this value over several periods. Exhibit 17-10 illustrates such a trend graph. This graph is of particular interest because it tracks all environmental costs and not just non-value-added environmental costs. If eco efficient decisions are being made, we should observe a reduction in total environmental costs. This implies that there is a favorable trade-off between investments in environmentally related prevention activities and reduction of environmental failure costs. The trend should be downward, as eco efficient investments are made.