126. In Egypt, in 1970, the Aswan Dam was completed. By preventing the annual flood of the Nile (thereby providing millions of acres of arable land) and by providing electricity, the dam was expected to raise the living standard of the Egyptian people-and it has. However, it has also led to a rise in the water table which causes Egypt's limestone structures, including the pyramids, to absorb more salt water and to suffer serious erosion from crystallized salts. Combined with air pollution and traffic vibration, this erosion is turning the pyramids to dust. Economists analyze this type of problem with the concept of 127. A factory pours its toxic wastewater into a nearby river, and as a result, the residents of a downstream community experience high rates of illness and birth defects. The economic problem illustrated by this example is
126. In Egypt, in 1970, the Aswan Dam was completed. By preventing the annual flood of the Nile (thereby providing millions of acres of arable land) and by providing electricity, the dam was expected to raise the living standard of the Egyptian people-and it has. However, it has also led to a rise in the water table which causes Egypt's limestone structures, including the pyramids, to absorb more salt water and to suffer serious erosion from crystallized salts. Combined with air pollution and traffic vibration, this erosion is turning the pyramids to dust. Economists analyze this type of problem with the concept of 127. A factory pours its toxic wastewater into a nearby river, and as a result, the residents of a downstream community experience high rates of illness and birth defects. The economic problem illustrated by this example is