Add economics to the growing list of subjects - including geography, writing, foreign language, science, and mathematics - on which American students are appallingly ignorant.

Just how ignorant can be seen from a nationwide survey sponsored by the Joint Council on Economic Education whose results were released this week. Among other findings in the survey of 8,205 11th- and 12th-grade students in public and private high schools in 42 states:- Only a third were able to define inflation.

- Only 34 percent could correctly define profits as "revenues minus costs."

- Just 39 percent selected the correct definition of Gross National Product: "the market value of the nations's output of final goods and services."

- A mere 45 percent realized that government deficits result when spending exceeds tax revenues.

- Less than half - 47.7 percent - knew that "economic demand" for a product refers to how much people are willing and able to buy at each price.

Though the survey that produced these results is described as the first to document the lack of simple economic knowledge among American students, the extent of economic illiteracy in this country should not have come as a surprise.

It should have been apparent from the fact that polls regularly show that even adult Americans estimate corporate profits to be 25 percent higher than they actually are.

It should have been apparent from the fact that economics courses are regularly left off the list of required subjects in college as well as high school.

It also should have been apparent from the fact that few high school teachers are qualified to teach classes in economics.

To describe these shortcomings is to prescribe the remedy for America's economic illiteracy. As long as Americans remain in the dark about economics, they short-change themselves by being less than wise consumers, by being unable to fully appreciate and defend the free enterprise system that has produced this nation's wealth, and by being unable to pass intelligent judgment on various government programs and policies dealing with the economy.

Better economic education, then, should be considered not just a luxury but a necessity.