Washington maintained its status last year as the nation's most affluent retail market, with a spendable income per household of $22.991 that was 33 percent above the national average.

According to Sales and Marketing Management magazine, which compiles such figures on after-tax income each year for a national survey, the average household here accounted for $10.391 of retail purchases in 1977. The area also had the highest per capita spendable income in the United States at $7.964 for every woman, man and child.

The annual report reflects the startling growth of incomes in the federal city and its suburbs, with more than 3 million residents and just over 1 million households. For the average household here, available money to spend after taxes has jumped 155.5 percent in the past decade.

Northern Virginia counties and cities in the metropolitan area accounted for only 20 percent of Virginia's population but 30 percent of the state's spendable income and 24 percent of sales in 1977: the area's Maryland counties had 32 percent of that state's population, 39 percent of income and 38 percent of sales.

Such are the statistic published in the latest edition of Sales and Marketing Management magazine's annual "survey of buying power" across America, now being printed and mailed to subscribers.

Of the nation's ten largest urban areas surrounding a central city, the Washington area ranks first in what the magazine terms household buying income. The only other metropolitan areas where per-household buying income exceeds $20,000 a year are Detroit ($22,277), Chicago ($21,891) and Houston ($20,435).

On Long Island Nassau and Suffolk counties (with no central city and fewer households than Houston) have a per-household spendable income of $23,993 but there's some dispute about whether the two New York counties add up to a metropolitan until comparable to other urban complexes.

In the Washington area, data compiled by Sales and Marketing Management reflects in numbers and percentages the significant population and social trends here over the past decade.

For example, the magazine's figures shown that in every single year since 1967 the dominance of the area's retail markets by the suburbs has increased and the District's share has declined. As the suburbs have grown, they have become ever more important sections of the states of Maryland and Virginia.

There are statistics for sociologists to mine, too. For example, the Washington area ranks only ninth among the top ten markets in per-household grocery store sales, and restaurant sales at $1.1 billion a year equal more than half the annual grocery store volume of $2.1 billion, showing a marked propensity to eat out.

And then there are drug store sales. The Washington area is No. 1 in the nation with per-household annual drug store purchases of $502, up 93 percent in the past decade. Washingtonians also love to furnish homes: Furniture and appliance sales soared 165 percent in the past decade, the largest increase among categories of family spending here.

Among other figures compiled from the annual survey:

The number of area households jumped by 142.800 or 15.5 percent since the 1970 census, the third highest rate of household growth in the top ten markets. Total spendable income in 1977 was in excess of $24.5 billion, up 96 percent from 1970.

While per-household spendable income rose 70 percent since 1970 the area cost of living increased 56.1 percent.

The area's three Maryland countries (Montgomery, Prince Georges, Charles) accounted for about half the increase in households since 1970. But Fairfax County in Virginia showed the largest growth among single jurisdictions (up 39,300 households).

In average spendable hosehold income, Fairfax continues in first place at $27,582 with Montgomery second, at $26,406.

In rate of growth, both households and income, the largest relative gains have been made in three rural counties most distant from the District - Prince William, Loudoun and Charles.

D.C. average household income after taxes last year was $19,425 - 12 percent above the U.S. average and higher than the states of Maryland ($18,672) or Virginia ($17,276). Despite a population dip, the number of households in the city rose 6 percent since 1970. D.C. retail sales last year, at $2.15 billion, accounted for 19 percent of the areawide total of $11.1 billion.

In the past five years, areawide retail sales rose 47 percent (D.C., up 20 percent): food store sales rose 45 percent (D.C., up 30.5 percent) and general merchandise sales rose 40 percent (but D.C. declined by 2.4 percent).

Sales and Marketing Management estimated area population last Jan. 1 at 3,072 million, up 4.4 percent since the 1970 census. The District's population declined over this period by some 70,000 to under 700,000.