Consumer spending dipped in April when President Carter withdrew backing for the $50 rebate and auto manufacturers ended sales promotions, the Commerce Department reported yesterday.

Retail Sales had posted gains in the two previous Aprils.

The department estimated total retail sales at a seasonally adjusted $59,397 billion in April, down less than one-tenth of a per cent from the reported $59.4 billion in sales for March.

The decline would have been deeper except for a downward revision of $200 million in last month's preliminary estimate of sales for March.

Meanwhile, the Commerce Department also said yesterday that the average American's personal income grew by 9.1 per cent in 1976, well above the inflation rate. In a report on personal income, the department said per capita income nationwide increased from $5,903 in 1975 to $6,441 in 1976.

Consumer spending slid 2 per cent during the freezing weather of February, then recovered in March. But retail sales began to weaken in April when the outlook for the $50 income tax rebate dimmed in Congress. Then sales dropped in late April after the administration withdrew support for the rebate portion of its economic stimulus package.

Carter began discussions of a rebate following the November election, and consumer spending rose strongly in December. The new administration's economic advisers, led by Charles Schultze, said the gain was evidence consumers were "spending their rebate."

Schultze's analysis held up during the first three months of 1977 when consumers dipped into their savings accounts for spending at a $6 billion annual rate, apparently expecting the money to be restored through the tax rebate that would have equaled $200 for a family of four.

But withdrawal of the rebate was not the only spending disincentive for consumers in April. Thousands of Americans had to pay their income taxes, and auto manufacturers ended their sales promotions that offered discounts of several hundred dollars on new cars.

The commerce department said retail sales would be up 1 per cent from March if car and truck sales were not considered. Because of weaker car and truck sales, consumer spending for durable goods fell 2 per cent from March.

"The gain in personal income in all but five states exceeded the rise in consumer prices," said Robert B. Bretzfelder of the Bureau of Economic Analysis in discussing 1976 personal income. Consumer prices increased by 4.8 per cent in 1976, although the pace of inflation is picking up in 1977.

The highest per capita income was $10,178 in Alaska, while the smallest was $4,575 in Mississippi.

States with high per capita incomes generally are concentrated in the Northeast and Far West, while those with low incomes are in the Southeast.

Per capita income increased the fastest in Michigan at 13 per cent. Main at 12.5 per cent and Mississippi at 12.25 per cent.

Reflecting sharp declines in farm income, per capita income declined 6.5 per cent in North Dakota and 2.5 per cent in South Dakota.

The growth rates in Hawaii (4.7 per cent), Montana (3.1) and Nebraska (2.2) trailed the inflation rate.

A labor union economist argued yesterday that the average worker's gains over inflation in 1976 were not enough to make up for earlier setbacks. In 1975, the average worker's personal income rose by 7.6 per cent, just a bit above the 7 per cent increase in the consumer price index. In 1974, personal income rose by less than the 12.2 per cent boost in the consumer price index.

The definition of personal income includes wages and salaries, interest, dividends, and Social Security benefits. Money saved by homeowners who otherwise would have paid rent also is counted as income.

Last year, weekly wages increased about 7.2 per cent, the report said.

Contributions to pension funds and Social Security are deducted from the income figure. It is calculated before taxes are paid.

Per capita income is all of the country's personal income divided by the total population.

Here is a list of regions and states with their per capita income in 1976, and the percentage change from 1975:

New England: the region $6,590, up 8.4; Connecticut $7,373, up 5.9; Maine $5,385, up 12.5; Massachusetts $6,585, up 8.6; New Hampshire $5,973, up 11.1; Rhode Island $6,498, up 10.4; Vermont 5,480, up 10.4.

Mideast: $6,975, up 8.5; Delaware, $7,290 up 8.1; District of Columbia $8,648, up 11.6; Maryland $7,036, up 8.9; New Jersey, $7,269 up 8.2; New York $7,100, up 8.2; Pennsylvania $6,466, up 8.8.

Great Lakes: $6,793 up 10.9; Illinois $7,432, up 9.4; Indiana $6,257, up 10.6; Michigan $6,994, up 13.4; Ohio $6,432, up 10.3; Wisconsin $6,293, up 10.9.

Plains: $6,130, up 9.5; Iowa, 6,439, up 6.0; Kansas $6,495, up 7.4; Minnesota $6,153, up 5.8; Missouri $6,005, up 9.4; Nebraska $6,240, up 2.2; North Dakota $5,400, down 6.6; South Dakota a $4,796, down 2.6.

Southeast: $5,544, up 9.7; Alabama $5,105, up 9.8; Arkansas $5,073, up 9.9; Florida $6,108, up 8.3; Georgia $5,571, up 9.8; Kentucky $5,423, up 11.0; Louisiana $5,386, up 10.0; Mississippi $4,575, up 12.2; North Carolina $5,409, up 9.9; South Carolina $5,126, up 11.1; Tennessee $5,432, up 10.7; Virginia $6,276, up 8.5; West Virginia $5,394, up 9.1.

Southwest: $6,040, up 10.1; Arizona $5,817, up 9.4; New Mexico $5,213, up 9.3; Oklahoma $5,657, up 7.6; Texas $6,243, up 10.8.

Rocky Mountains: $6,072, up 8.7; Colorado $6,503, up 8.4; Idaho $5,726, up 10.6; Montana $5,600, up 3.1; Utah $5,482, up 11.0; Wyoming $6,723, up 10.6.

Far West: $7,048, up 8.6; California $7,164, up 8.6; Nevada $7,337, up 10.0; Oregon $6,331, up 10.1; Washington $6,772,, up 7.8; Alaska $10,178, up 6.7 Hawaii $5,969, up 4.7.