In Washington, trade associations are Big Business.

With the magnetism that is a natural adjunct to a national capital, Washington has attracted more than 900 new associations of all types during the past decade. Leaving their time-honored Chicago and New York homes, more are moving in all the time.

In fact, the association business constitutes the city's third largest employer after the federal government and tourism, says James P. Low, president of the American Society of Association Executives (ASAE), the super species of the association kingdom.

The 2,500 trade associations and profesional groups based in metropolitan Washington -- about a third of all national associations -- account for upwards of 87,000 employes and dole out an aggregate payroll of $2 billion yearly. Their combined budgets total more than $4 billion, making the association business one of the largest here.

Research of ASAE shows that the typical association based in the D.C. region has an annual budget of $1.6 million and a staff of 20. But some groups, like the American Bankers Associations, have staffs that number in the hundreds and budgets that top $20 million.

About 50 printing establishments in the District and outlying suburbs live off the associations' $250 million annual printing needs. And the organizations farmed out more than $47 million in data processing work last year.

The associations' marble-sick buildings are a tipoff to their roles. Beyond their traditional lobbying function, they are becoming industury's status seekers in the broadest sense. They see Washington as a haven in which to achieve their goal -- greater responsive to members.

At this week's ASAE convention and exposition, to be attended by more than one-fifth of ASAE's 10,000 members, the push will be on to convince still more association executives that Washington is the center of the action.

Much of the recent growth is taking place at the expense of New York City, long heralded as a mecca for trade association headquarters. About five years ago, Washington forced New York to give up its throne in this area so that today, not more than 2,000 associations call New York their home.

Trade associations come to Washington for all manner of reasons and bring a wide variety of activities with them. But by far the dominant motive is to be closer to government.

Most associations simply want to keep closer watch on proposed regulations affecting the industuries they represent.

Consumer and product safety measures are of particular concern to the National Electrical Manufacturers Association NEMA), which moved here from New York in 1977. NEMA's 550 members manufacturers of heavy electrical products like motors and generators, told their association to move to D.C. to establish closer liaison with the Department of Energy.

"You just can't respond as quickly when you're sitting on Fifth Avenue in New York as when you're a mile from the Capital," said Dan Shipp, NEMA's public affairs director. "If we need to be at a hearing, it's a cab ride, not a jet ride, away."

The National Restaurant Association, representing some 225,000 eating establishments, left Chicago to set up home base here last November. The association in closest proximity to the Capitol, NRA says since the move, it has been more involved in legislation determining minimum wages and capital equipment depreciation rates.

"When 70 percent of our members tell us representation in Washington is the most important thing we do for them, what else could we do but move?" said Kelly Johnston, director of communications for NRA.

Beyond the government-business link that is ever more perceptible, there exists a growing synergism between trade associations that accounts for some organizations' move to Washington.

By joining forces for coalition lobbying, associations representing like industries in the private sector "get in bed together and have a much stronger force," said ASAE's Low, who has been in the trade association business here for 26 years.

For example, the so-called Road Gang, a group of associations representing everything from automobile producers to truckers, was effecitve in lobbying for deregulation of the trucking industury.

The Food Group is another coalition of associations representing canneries, grocery owners, fisheries and vegetable producers that lobbies as a unit.

The Aluminum Association, representing primary producers of aluminum, moved here from New York in 1977 to lobby on energy-related issues with associations representing steel, paper and cement industries.

Washington business leaders feel that the reasons which have already brought the 2,501 national associations here apply with equal force to many organizations located elsewhere. The Board of Trade is intent on driving this point home to more and more trade association executives.

The Board is spending about $150,000 yearly on its newest campaign, "Greater Washington: The Association's Capital," which is targated to associations with staffs of 10 or more people and budgets in excess of $250,000.

Among those the board is after are the American Society for Trade and Development, now in Madison, Wis., and the American Hotel and Motel Association (AH&MA) in New York.

AH&MA has just initiated a study to see if D.C. might be a better headquarters location. Proposed plans for gasoline rationing or weekend gas station closings, which would harm the tourism industry, incited AH&MA directors to consider the move.

As Washington provides a convenient center stage for the associations, they in turn fuel the Washington economy.

Officials at the Board of Trade cite two major business benefits these groups provide the community. One is that trade association jobs are "basic empolyment, like Federal jobs.

Associations also furnish a continuing stimulus for the tourist and convention trade. For instance, ASAE's convention this week will bring $5 million to the city. Following completion of the new convention center, many Washington-based associations plan to move their annual conventions to D.C. from New York, Chicago and San Francisco.

The Board of Trade forecasts that by 1990, convention business from associations alone will total more than $600 million.

Even today, despite the recession, associations are growing rapidly.

"Associations are inflation-proof. The auto dealers are a great example. Now that the dealers are in trouble, they really need their associations to find support in Washington," Low said.

A ASAE survey completed recently showed that, of 40 percent increased dues this year. Of those that raised dues, only 10 percent lost members.

Typically, an association planning a move to Washington sets up a branch office here first to make government contacts, helps locate office space, negotiates leases and scouts around for homes for the association's executives.

ASAE's subsidiary corporation called Association Relocation Services, Inc., assists newcomers with these tasks.

Often, no more than 10 percent of an association's original home staff makes the move, forcing many associations to build the new Washington office staff from scratch.

"Still, it's really worth it to move here," said Low, who likens the immigration of associations to Washington like a rapidly multiplying flu germ. "It's catching and a lot of executives are catching it and catching on."