Since the stock market plunged three weeks ago, Americans have been transfixed by the movements of the Dow Jones Industrial Average and other financial indicators. But Mykl and Natalie Barron are monitoring something much closer to home: the parking lot at Capital Plaza Mall in Landover, outside their Dunkin' Donuts franchise, where traffic seems puzzlingly slack.

"I see a change and I can't identify what it is, but I know that it has directly affected me," Mykl Barron said in late October of a drop in nighttime doughnut sales. "Maybe it's related to consumer confidence, but maybe it's the {sunny} weather. It's on gloomy days that people need sugar to brighten their outlook."

Just as the Barrons are trying, from the vantage point of a doughnut shop, to second-guess the reaction of the national economy to a record market drop, millions of other Americans are in a watchful stage, weighing whether to keep spending money or to tighten their belts, choices that, taken together, will help determine how the economy fares in coming months.

For all its fury, the impact of Black Monday -- Oct. 19 when the Dow Jones Industrial Average of 30 stocks plunged 508 points -- on American households and businesses was widely variable.

Robert Deane, of Silver Spring, an economist and father of five making $82,000 a year, lost heavily in the stock market plunge, thanks in part to panic selling and buying of stocks. He has put off indefinitely plans for household improvements.

R. Carl Benna, a manufacturer of modular homes in Point of Rocks, Md., was forced by the market drop to put off plans to take his company public next year by selling shares to investors. "We just sat by the phone most of the afternoon in disbelief," he said. "We just saw a lot of things going down the drain." An optimist, Benna said he still foresees expanding his business, albeit more slowly.

By contrast, John and Helen Clark of Oakton, Va., with combined annual income of $100,000, shrewdly sold their stocks before the plunge and now spy a new opportunity: They may invest in real estate. But even before the crash, they had had second thoughts about buying on credit. "This may scare people and get them to slow down," said Helen Clark, "and maybe it's time."

With the economy having survived the shock of Oct. 19, a crucial question is whether it will suffer from the aftereffects. Will consumers keep spending with confidence? Or will they grow cautious, delivering an aftershock of their own to the system?

To answer these questions, The Washington Post has chosen a dozen consumers and business managers in the Washington area -- people such as the Barrons, the Clarks, Benna and Deane -- who will be interviewed regularly in the aftermath of the biggest drop in stock market history. Analysts say that the next few months will determine the impact of the plunge on the psychology and choices of millions of people like them -- and, by extension, on that pivotal indicator known as consumer confidence.

"The immediate or direct impact {of the plunge} is rather small," said Richard Curtin, director of the University of Michigan's widely cited consumer survey. "But the indirect impacts are larger and take time to develop. If, for example, we see reports of higher unemployment, there could be real damage to confidence" and the overall economy.

Already, he said, the survey has recorded a shift. In August, consumers said they wondered whether economic growth would slow down or speed up. After the market fell, he said, they were asking whether the economy would slide into recession or merely slow down. "Their choices are essentially negative ones now," Curtin said.

Three weeks after Black Monday, the people and businesses in The Post's survey have absorbed Wall Street's record jolt with a mere shudder. They said they are more wary than before, but basically confident that the economy is sound.

Most said they weathered the shock in part because they already had begun to brace for a downturn, out of concern over the budget and trade deficits and a sense of drift in Washington. More affluent than the average consumer, they tend to feel cushioned from economic swings.

Some focus on the effect of the plunge on their spending patterns, others on how to shift their investments. Both reactions could have far-reaching implications, if mirrored by millions of consumers.

"I know the markets are intertwined and that the problem can come back at you like a tidal wave," John Clark said. " . . . The crash was a big shock, the walls rocked, but I didn't feel it was the one that cracks the foundation."Housing Business Expansion Put on Hold

Point of Rocks, Md., about 40 miles northwest of Washington, appears to be a world away from Wall Street. But the market set back R. Carl Benna's big plans for his $80 million North American Housing Corp. He wanted to sell shares to the public next year, to raise $15 million, to build a new factory and buy new equipment. Benna and 40 employes were also hurt because their pension fund, terminated last March, had been invested in mutual funds.

But Benna said he discerned a silver lining for his company in the cloud over Wall Street. With interest rates down and stock prices unsteady, he predicted people will say: "Let's get back to tangible, real things." Things such as new houses, for example. He said he has seen no impact on this quarter's sales and his company continues to work on a backlog of orders.

With his expansion on hold, Benna, a self-described cautious businessman accustomed to swings in the housing market, remained bullish. Now, he said, the growth "will take five years if everything falls into place perfectly."

Similarly, at the No. 1 Buick dealership in the Washington area -- Peacock Buick in Tysons Corner -- it's damn the Dow Jones average, full speed ahead.

Though analysts said car sales would be the first to suffer, general sales manager Dick Bailey finished October with 92 new cars sold, compared with 88 in September. (That was down, however, from last year's October total of 108, when interest rates were lower.)

Bailey, who festoons his showroom with red, white and blue "Made in the USA" banners, has made only one business change since Black Monday: He canceled one of his favorite television ads, the one showing the opening bell on Wall Street and the message, "America, land of opportunity."

But he hasn't trimmed orders and doesn't plan to, though Buick buyers are in the income range likely to have had money in the stock market. The Saturday after Black Monday, George Reese, a program analyst for PRC Realty Systems, explained why he was buying a $12,000 Buick Century from Bailey:

"I must admit I got a little reluctant when the special bulletin came on the TV, but the more I thought about it, the more I just decided this is something we really need."

The news was much the same on K Street, at Sovran Bank/DC National, sixth-largest in Washington. Bank president and chief executive officer Robert P. Pincus reported slightly more than 2 percent growth in commercial and consumer loans for October, a rate consistent with the bank's annual average of 27 percent.

After reviewing all loans secured in any part by stocks, Albert A. D'Alessandro, head of commercial loans, said none required more collateral. No new loans have fallen through, and new applications haven't slackened, he said.

The two bank officers were a portrait in optimism last week. D'Alessandro was on his way to the closing of a $9 million radio station acquisition, in which the bank had a $5 million loan. Pincus, whose own retirement fund and stocks lost some value in the plunge, had just returned from a downtown clothier, where he bought a suit and sport jacket without a thought about his losses.

"I'm still very optimistic that what we've seen is an adjustment, not a panic," Pincus said.Family Is Watching Every Penny

The day after the Dow Jones industrial averge crashed 508 points, Robert Deane, chief economist for the American Health Care Association, hit the panic button and began trading a $150,000 mutual fund in hopes of cutting his losses. "My clever trading cost me about $12,000," said a rueful Deane, who sold too low and bought too high.

With five children, a wife, an $82,000-a-year income and an unusually high rate of savings, the Silver Spring family already was watching every penny. Their six-bedroom house, bought in 1974 for $76,000, is almost paid off and their two cars have been driven more than 60,000 miles apiece.

Now, said Deane, to pay for a beach home, tithing to the Mormon Church, routine bills and other obligations, they must forgo plans to put a new roof on the patio, refurbish living room furniture and replace some windows.

"My oldest son said, 'There goes the Mercedes,' " said Deane's wife, Diane.

Deane said he blames only himself for his losses and would not have shelved the renovations from lack of confidence in the fundamentals of the economy. Once burned, he has transferred management of his investments to an adviser, David Petersen, saying that he views the market as unstable and prone to more drops.

But Deane confessed: "I pray it happens {another drop}, because I'm jumping back in. I want to be a winner for once."Couple Plans No Change in Life Style

Tom Vojir, a manager of computer systems for Magnavox Electronics Systems in Leesburg, knows he lost some of his $65,000 in investments on Black Monday, but hasn't even bothered to total the damage.

"I just took what happened in the stock market as a confirming sign that the economy was in bad shape, compared with what it could be," Vojir said. ". . . I assume my gold went up and the others {investments} went down . . . . I don't watch it day-to-day."

Vojir and his wife, Hazel, a health claims analyst for the National Association of Letter Carriers, have combined earnings of $80,000 a year.

They live comfortably, but not lavishly, in suburban Sterling, Va., and said they plan no change in their life style, which includes vacations in Hawaii and Florida, fast-food dinners, occasional indulgences like a wood inlay bought in Hawaii and home improvements. They are talking about a $35,000 home remodeling, new central air conditioning and a hot water tank.

In general, they said, they have less to lose from the crash than if defense contracting dropped off.

In fact, Vojir sees some good in the stock market's drop. An avid investor, he has stuck to mutual funds and other instruments because of their safety. But the market's decline may give him an opening to dabble in riskier, single-issue stocks. He has an eye on natural resources stocks, including Texaco and Amoco, he said.

"The drop in the market won't change my consumer spending, but it may change my investing," he said.Living as if Plunge Was 2 Years Ago

Black Monday may as well have occurred two years ago for Diane and Jerry Jeffers of Fairfax County. That was when their infant son, Matthew, born with water on the brain, had a stroke, followed by seizures, continuing complications and enormous medical bills.

Today, they live as if the economy had crashed. Diane left her job to care for Matthew and his two healthy brothers, leaving Jerry's job as a United Parcel Service deliveryman -- $34,000 a year with overtime -- and her $15,000 disability to cover medical bills of about $100,000 beyond their insurance coverage.

They haven't gone out alone together for a year and a half, and Diane saves by clipping coupons, comparison-shopping at three stores, Christmas shopping in the summer and buying diapers only when they are on special sale.

"I was going to get a lawn service, but couldn't justify spending $40 a month," Jerry said. "Our pediatrician would rather get paid."

For all that, the market still took a toll on the Jeffers' expectations. Diane has iced plans to start a consulting firm for parents of fragile children, saying, "it would be hard to get it going if the economy stayed worse."

She also said she worries that a falling dollar will drive prices up. But Jerry is optimistic. "As long as I have that steady income, we'll be comfortable," he said.

A friend's husband lost $12,000 in the market, Jerry said, "and that's all she talks about. {But} after going through what we've been through with this little guy . . . losing money doesn't seem that bad."Will It Be the Doughnut or the Hole?

A year ago, Mykl and Natalie Barron had what Mykl calls a "typical Yuppie life." He was a planner for Metro, she an accountant for GEICO. They had a house in Baltimore, combined income of $55,000, the freedom to see movies whenever they wanted.

But last March, the two swore off all that, and bought into a Dunkin' Donuts with help from a Maryland program assisting minority franchises. Now their total annual income is about $25,000, near the average in the neighborhood around their shop, next to Capital Plaza Mall off the Baltimore-Washington Parkway.

The Barrons have a double income and no children, but without the luxuries often associated with that life. They live with Mykl's parents in Lanham, at least until they sell the Baltimore house, and drive a car they had hoped to replace.

Their big worry is not the stock market but whether they will emerge from this venture with the doughnut or the hole. Any swings in the economy could play a key role, they said, but they don't expect to be hurt. "If somebody is going to treat themselves to anything, it'll be coffee and a doughnut," Mykl Barron said.

"I heard the average was down 508 points that day, {but} it didn't dawn on me that that was significant to me," he said. "People were still working. I didn't see everyone in soup lines or unemployed. I didn't expect any direct impact on the business."

While the average neighbor of Capitol Plaza Mall was not a big stock market player -- or loser -- Mykl Barron, trained as a community planner, said lower-middle income families are quick to cut back when the economy turns precarious. "If people don't shop at the mall," he said, "they don't stop by here."

For now, they have cut their nighttime baking by 25 percent, but with cool weather on the way, they bank on doughnut cravings to conquer all adversity.Ex-Marine Left Stock Market Early

John Clark, a retired Marine Corps colonel who started a company two years ago, escaped unscathed. He pulled his money out of the stock market "some months ago when it appeared {stock values were} simply getting too high."

Now he and his wife, Helen, say they expect some downturn in the economy, but not enough to stop their search for new opportunities. They are looking for a town house to rent out, particularly in light of falling interest rates and a general housing slowdown.

With combined incomes of $100,000 -- he from his company that helps American and certain foreign firms develop business with the federal government, she as a contract administrator for Honeywell -- they said they have always been careful about money, and do not expect to change in the aftermath of the plunge.

John Clark has two grown children from an earlier marriage. And both he and Helen have a pioneer-style spirit about their finances and the economy. "If it all goes away," he said, "we'll just start over."

Analysts caution that there is a lag between shocks such as a market plunge and consumer reaction. People who made major purchases in October likely planned them in the more bullish months that preceded Black Monday. Those making them in November and December may see things differently.

In the words of Dick Bailey, Peacock Buick's sales manager, a seasoned observer of consumers: "We'll know in 60 days if these analysts are right."

Staff writer Karlyn Barker contributed to this report.