A new U.S. Census Bureau report confirms the often-made charge that blacks suffer disproportionate job and income losses during periods of economic decline.

The report, released yesterday, also says that economic downturns have played a major role in slowing black progress toward role in slowing black progress toward full social and economic equality with white Americans.

"Blacks have become a people whose progress toward fulfillment of the Amercian dream has been erratic and uneven," the Census Bureau said in releasing its report.

"The report shows that in almost every area, progress has been noted. Some however, such as income, employment and health, have followed an erratic pattern of development with significant interruptions of upward mobility," the bureau said.

The report is titled "The Social and Economic Status of the Black Population in the United States: An Historical View, 1790-1978." It attempts to present a detailed statistical portrait of the black American experience form slavery to emancipation to modern times.

There was little change in the black economic and social condition until the latter part of the 19th century. Some moderate progress was made in the first three decades of the 20th century. However, those black gains were "substantially diminished" by The Great Depression of the 1930s, the report said.

World War II, the Korean war and the period in between brought new gains for blacks, but they were largely wiped our by the recession of the late 1950s.

Between 1964 and 1969, median black family income rose by about 36 percent, from $5,920 to $8,073 annually. But the economic declines of the 1970s eroded these gains, and in 1974 black median family income was $7,810 annually, about 3 percent below its 1969 level.

The stop-and-go black economic progree is more graphically illustrated in employment, according to the report.

For example, black employment grew at a faster rate than white employment from 1954 to 1965 - about 24 percent for blacks and 18 percent for whites. Since 1965, relative gains in rates of employment for blacks and whites have been just about even, about 28 percent.

However, the report said that for most of the period from 1948 to mid-1978, the unemployment rate for blacks generally has remained at least double that for whites.

Loss of employment meant loss of income. And that loss, according to the report, is reflected in the continuing, general disparity between black and white median incomes.

For example, in 1974 the median family income of blacks and other minorities was about 62 percent of the median income for white families, according to the report.

However, the report noted that at least one segment of the nation's black population - young, married, two-income couples in the North & West - managed to achieve economic equality with their white counterparts.

With 45 percent of young black wives working year-round, compared to 33 percent of white wives in the same category, young black husband-wife teams in the North and West earned median family incomes of $16,715 annually in 1976. Similar white families, that same year, earned median incomes of $16,691, the report said.