Ronald Reagan is expected to run his Executive Branch like General Motors or some other big corporation, and that's not necessarily bad.

However, if the business of running his inaugural is an indication of what to expect over the next four to eight years, it may be more difficult than in the past to find out what's going on.

In terms of local business, a presidential inauguration is one of the biggest events in this town, normally pumping enough new life into the area's economy to more than make up for the lackluster previous year.

This time around, there are forecasts that history will be repeated. But there is virtually no solid evidence or base of statistics. The complex inaugural organization, headed by Washington public relations executive Robert Gray and Los Angeles investor Charles Wick, is unable to say what companies have received contracts for inaugural work.

There are no reports on how much has been donated and from whom, in the form of gifts, money, services or loaned executives. More than $9 million was advanced in interest-free loans to the inaugural committee from corporations and others.Again, no information is available on this aid, although Atlantic Richfield Co. has said it loaned $50,000.

To a large extent, this situation is understandable. In effect, Gray and Wick had to set up overnight what amounts to a $10 million business; (estimates of the inauguration's cost have ranged from $8 million to more than $10 million, compared with $3.5 million for President Carter). The loans will be repaid with revenues from tickets sold to inaugural events. Gray told the National Press Club last week that: "We don't expect a deficit at all."

What's more, the business they started has a very short life, incapable of attracting a staff concerned about careers in those particular posts, (although some certainly are hoping for work in a GOP administration).

Indeed, the major untold story about the inaugural is the army of several thousand volunteers -- individual citizens plus private sector employes loaned to the inaugural committee by their firms -- who have done most of the work. Some Washingtonians left their permanent desks for inaugural work in November and haven't returned. For some, Christmas was their only day off to date.

Some of the volunteer talent has been the best in the business. Former Washington restaurateurs Paul Young and Duke Zeibert -- both recent departures from establishments that carried their names for years -- were seen one day in a cafeteria line, definitely not their usual ambiance. They were taking some time out from consulting work to the inaugural folks on catering.

Such devotion should not be interpreted narrowly as evidence of tremendous support for Reagan, although he clearly was the favored candidate in last November's contest among Washington business leaders. Rather, as one official of a Washington-based corporation said last week: "This is nothing political. I've never voted for anyone but a Democrat. I'm doing this because a friend asked me . . . this is an occasion for the whole nation, and I've helped out some."

Similarly, Washington stores are decorated for this week's inaugural in much the same nonpartisan fashion as four years ago. The Greater Washington Board of Trade has been selling decoration kits, containing a 2-by-3-foot picture of Reagan and Vice President-elect George Bush, a 3-foot square red, white and blue fan, and other decorative strips for $35 apiece. Large stores have done elaborate decorations on their own.

In addition, the Board of Trade and the public relations firm of Poretz & Jaffe compiled a fact book on the Washington area and its business community, to be distributed to more than 1,100 members of the national press here for inauguration events. The Reagan inaugural offices have faced a difficult task in answering all the local, national and international press inquiries and many questions simply have not been answered.

The best, and apparently only, guide to business activity here during inauguration week is the room occupancy levels at the area's hotels. There are some 35,000 hotel rooms in the entire metropolitan area and virtually every room is occupied today and tomorrow. The Mayflower Hotel, for example, was booked solid by the day after the election.

Austin Kenny, executive vice president of the Washington Convention and Visitors Association, estimates that if each person registered at area hotels stays four days, he or she will spend $500 for a hotel room, three meals a day, transportation and souvenirs.

An estimated 50,000 to 70,000 persons who do not live in the area are expected to be in town this morning for the inaugural events and using Kenny's figures, that translates into $25 million to $35 million in direct spending. And since each dollar turns over two or three times as it trickles down in the area economy, the total economic impact of Reagan's inauguration here could well be in the range of $75 million.

But these figures don't tell us about spending by area residents, (gown purchases for the balls and tux and limousine rentals have been booming businesses, for example); spending by the Inaugural Committee and outlays by area businesses to prepare for Inauguration Day.

The Capital Hilton Hotel is a good example. In effect, hotel officials led by general manager Frederick Kleisner saw an opportunity approaching to spruce up their 725-room complex in downtown Washington, opened in 1943 and the site of many a presidential dance on inauguration night. oHilton Hotels agreed to spend $661,300 on a massive renovation to be completed by inaugural week.

New dance floors were installed ($30,000) in the main ballrooms, where President Reagan is expected early on Tuesday night for one of eight big celebration dances throughout the area. The Capital Hilton also spent $111,000 for new ballroom carpeting; $95,000 for new landscaping; $182,000 on six new luxury suites; $49,000 for new uniforms that arrived last week; $39,000 for new china, glass, silver and linen; $35,000 on a new carpet for the Twigs restaurant and $99,000 to renovate the old Embassy Room.

Stars such as Xavier Cugat, Edith Piaf and Hildegarde all performed in the Embassy Room in its early years and the Capital Hilton is preparing for a big reopening.

One other example is American Telephone & Telegraph Co. Through its subsidiary Chesapeake & Potomac Telephone Co., the Bell System expects its workers to spend between 200,000 and 250,000 work hours to engineer, order, install, maintain and dismantle circuits and phones for the inaugural.

A C&P task force has been at work since last April, working with news media representatives and other customers to determine their needs this week. In an unprecedented move, C&P has doubled the audio and video capacity of its transmission facilities going out of Washington, using AT&T personnel from all over the nation to help. Now that's organization.