The Commerce Department yesterday unveiled a montage depicting what will happen to American incomes in the 1990s. Industry by industry, state by state and region by region the picture showed sharp variations across the sweep of the United States while leaving an overall impression of muted gains.

The department's Bureau of Economic Analysis, which updates its projections for income, employment and population changes every five years, concluded that on average each person's income will rise 1.23 percent a year between 1988 and 2000, compared with 1.53 percent annually between 1979 and 1988.

That seemingly small decline in growth, after adjustment for inflation, would mean that over the 12 years, Americans would have nearly $1 trillion less for spending, saving or paying taxes than if the higher income growth rates of the previous nine years were maintained. U.S. personal income this year will be about $4.75 trillion.

In individual terms, per capita personal income in 1988 was $16,496. If the previous growth rate were maintained, that would go up to $19,795 in 2000, aside from any increase due to inflation. With the lower growth rate, however, it would rise to $19,102. In other words, per capita personal income is to be almost $700 less in 2000 than under the old rate.

Focusing on national averages, however, obscures sharp differences among states and regions.

New England, which left the rest of the nation struggling in its wake during most of the 1980s, is projected to have the slowest per capita income growth of any region, slightly less than 1 percent a year.

A similarly sharp change -- but for the better -- is in store for the four states of the Southwest region, according to the projections. Collapses of the farm and energy sectors of the economy, followed by devastation of the real estate market and bankruptcies of many financial institutions, put the Southwest near the bottom of the per capita income growth list during the 1979-88 years.

The predicted turnaround would put the Southwest on top, with projected income growth of 1.41 percent a year, up from only 0.5 percent in the earlier period.

According to the projections, which were published in the department's Survey of Current Business, most of the slower national growth in personal income will not be in workers' earnings. Rather, it will be mainly in other types of income, such as dividends, interest, rent and government transfer payments received by individuals, the survey article said.

Among industries, services will continue to have the largest gain in earnings, up 3.24 percent annually, but that is significantly lower than the 5.77 percent in the 1979-88 period.

The number of service jobs is expected to rise more than 2 percent a year, compared with an overall national figure of 1.12 percent.

Manufacturing earnings, surprisingly, are projected to do better, as the number of manufacturing jobs not only stops dropping, as they did between 1979 and 1988, but actually starts increasing. Instead of falling at an average annual rate of 0.83 percent, manufacturing employment is shown rising 0.27 percent annually.

Bureau of Economic Analysis economists said the slow growth projected for earnings in New England is centered on manufacturing and related service industries and on construction.

The coming slowdown in defense spending is expected to hit the region particularly hard.

In the Southwest, "strength in industries that manufacture transportation and electronic equipment will boost earnings growth," the article said.

At the same time, industries catering to tourists will do very well, adding to regional income growth.

Even with the relatively weak growth in New England, the region is already so far ahead of other areas that it will continue to have the highest average income of any region.

Connecticut, too, will still boast the highest per capita income of any state by the end of the century, 134 percent of the national average.

Mississippi, the lowest in the nation at 67 percent of the national average in 1988, will still be last at 69 percent in 2000, according to the projections.