THE WOMAN, I'll call her Margaret, was blunt: "The economy wrecked my marriage." She had married her busband "Bob" in 1975, when the economy was pretty good. Within five years, their marriage was in shreds.

The last decade has made divorce commonplace in America. But the rates of separation and divorce fluctuate more with the state of the economy among middle-class blacks than among whites, acording to a new study by Bart Landry, associate professor at the University of Maryland and a fellow at Woodrow Wilson International Center. Among blacks, the most important influences in marital status come from outside, rather than from within, the family. When the economy is bad, every American feels the stress, but black family breakup seems to increase at a more rapid rate.

That certainly was the case with Margaret and Bob. Each had come into the marriage debt-free, except for their respective car notes. They rented a home in the Maryland suburbs, and after about a year, decided to buy a house.

Both knew when they that Margaret would always have the larger paycheck, but neither one of them was bothered by this; each respected the other's uniqueness. It had not mattered that she had a college degree and a respected job; he'd traveled widely, had a good job and was a man of the world whom she respected.

For a couple of years, things went well. The couple contemplated the day they would have children and move to the larger house both wanted when their salaries inevitably increased.

But then problems surfaced: his work involved excessive traveling; her hours were erratic and would remain so for a couple of years. And though each found their respective jobs fulfilling, they did not have much time together.

Bob decided to change careers and find a job that permitted him to stay in Washington and that held economic promise. He chose real estate, enrolled in school to get the necessary license, promptly passed the examination and joined a realty firm as an associate.

Anticipating a six-month slow period, the couple budgeted in advance -- paying their house and car notes ahead of schedule.

Then the bottom fell out of the real estate market. Interest rates zoomed upwards. House prices went haywire. Homes were not selling. The price of gasoline skyrocketed.

In a couple of years, Bob had sold only a few houses, His income plummeted and he had to look for alternate employment. He could only find a part-time job that was far below his potential. As the economy worsened, the part-time job became a full-time one. Neither Bob nor Margarget was satisfied with the new arrangement.

"Because he was not bringing in much money I was losing respect for him and he was losing respect for himself," says Margaret. "He would stay away from home more because he did not want to be there because he could see the disappointment in me. We were living primarily from my paycheck -- from paycheck to paucheck. We stopped talking about our financial situation. I didn't think it was a conscious thing. I think he was looking for that kind of financial support but I know that was happening."

Finally, Margaret became so resentful that she approached him with her conflicts -- she was equating loss of respect for Bob with loss of love for him -- and his self-esteem had deopped so low that he hastily packed his bags and left their home the next day.

Such pressures from deteriorating economic positions, says Bart Landry, are common to all racial groups, but blacks are particularly vulnerable. And the horrible toll of divorce among blacks has resulted in the fact that more than 40 percent of all black families are now headed by women.

While Margaret was decidedly a member of the middle class, she understood that deprivation was close to certainty for black children where a woman is head of the household, and she wanted any future children they had to live with both parents. But when she was thinking about having a family, she and Bob were in too much economic stress to consider it realistically. "I couldn't see a future in it," she says.

Landry thinks middle-class black families have gone further than middle-class white families and even black working-class families in limiting the size of their families. "Again, the suspicion is that the economic factor is strongly at work here, particularly in the form of a very high rate of full-time employment among black middle class wives -- the result of economic need," he said. This is because black middle-class males annually earn $5,000 less on the average than white middle-class males, and since most black women were working already, they could not supplement the family income still further as many white women did by going to work during the past decade.

At a recent conference on the "structure of the new black middle-class family" at the Wilson Center, Landry, Hyland Lewis of the City University of New York and Joseph Berliner of Brandeis University expressed concern that the black middle class is limiting its family size for economic reasons. Given the rising cost of living, this may slow the growth of the black middle class itself, Landry feels.

What would reverse this trend? Getting more money to black families would certainly help. Getting the economy back on its feet would assist couples llike Margaret and Bob.

But this particular story has a happy ending. Bob and Margaret are a couple again, although he still hasn't found the job he needs. After several months of separation, they realized the pressures of the economy had to be less important than the realization that they loved each other. What started from his inability to help support his household and escalated into a lack of understanding and communication became translated into a loss of love. Being financially hard-pressed pushed this family to the edge, but they pulled back. Too many black middle-class couples, says Landry, are not so lucky.