Six European countries and Japan outstripped the average U.S. income of $21,100 last year, according to a recently released World Bank study.

The average Swiss earned the equivalent of $30,270 - the highest level in the world - the bank reported.Other countries among the world's top earners included Luxembourg with $24,860 average income, Finland at $22,060, Norway; $21,850, Sweden; $21,710 and Iceland, $21,240. The Japanese average was $23,730.

The income figures, which do not necessarily reflect living standards, were part of a bank study of 185 areas released Friday.

Part, but not all, of the difference was due to the low value of the dollar on world exchanges, a bank spokesman said.

Other factors affecting the variances are lower prices in the United States than in Japan, for example. Additionally, the average American enjoys more living space, a bigger car and eats a lot more meat than the average Japanese.

At the bottom of the list were impoverished Ethiopia and Tanzania, where the average citizen earned just $120 in 1989.

The report said average income declined for 900 million people in 64 areas, half of them in southern Africa. It added that figures were not complete but there also were decreases in about a dozen Latin American countries and almost as many in an area that included Europe, the Middle East and North Africa.

Nevertheless, the study found figures for 1987-1989 were an improvement over the 1980s as a whole.

About 2.4 billion people lived in countries where incomes were growing. They included the world's two most populous countries, China and India. In China the average rose to $360 from the previous year's $330, and the increase was from $340 to $350 in India.

However, more than half the world's population - 2.9 billion people - lived in countries where the average income was less than $500.

The bank said there was a close relation between incomes and other measures of living standards, noting that in those poorer countries only about 56 percent of the people knew how to read.

About 830 million lived in countries where the average income was higher than $6,000 and their literacy rate was over 95 percent.

"For those economies with life expectancy at birth of less than 50 years, the (individual) income averaged $280," the report noted, while "for economies in which life expectancy was more than 73 years, the average is around $18,000."