In 1960, when Sandra Day O'Connor was still an obscure attorney in private practice in Arizona, only 3.3 percent of her fellow lawyers and judges were women. By this summer, when she became the first woman nominated to the Supreme Court, that percentage had almost tripled.

O'Connor has potential counterparts in an increasing number of fields. Female accountants have more than doubled their percentages in the profession in the 20 years from 1960 to 1980. Bankers and bakers have more than doubled the percentages of women in their ranks, and the percentage of female doctors has nearly doubled in the same period.

Tinkers (or what the Labor Department calls mechanics), tailors and candlestick makers (craft workers) -- all have significantly more women on the job than ever before. And even among chiefs --managers and administrators -- women increased markedly in recent years.

Although the big picture and the big numbers remain stonily constant, with women still heavily concentrated in so-called female job ghettos such as the typing pool, government figures show small but meaningful signs of change in a number of previously male preserves.

During a sample five-year period in the mid-1970s when the total number of employed women increased 25 percent, their gains were dramatically higher in several areas: a 67 percent increase among managers and administrators, 81 percent among craft workers and 84 percent among non-farm laborers. (There had been so few women in these fields that, even with these advances, there were still only six female craft workers and 12 female laborers for every 100 males.)

The changes are to some extent the result of the huge influx of females into the labor force during a period when men, for a variety of reasons, have been working less. Thus women have had an increasing share of the total work force.

The differences occur primarily in the rising generation of working women. "The occupations of younger women are far different from the older generation," said Anne Young, an economist with the Bureau of Labor Statistics. For instance, a remarkable 64 percent of all women ages 25 to 34 were in the labor market in 1979.

"But it's going to take a long time for this to permeate the labor force," Young said. "And it will depend on whether these younger women who are claiming the so-called non-traditional jobs will stick with them," maintain the job stability, build up seniority and otherwise behave in the ways that enable men to earn higher salaries.

While younger women are staying in school longer, delaying marriage and childbearing more than earlier generations, it is changes in their behavior after they marry and begin families that are causing the real difference between their work lives and those of their mothers, according to labor economist Linda Waite of the Rand Corp.

In the past, "virtually all women left the labor force when they had a child," she noted in a recent study for the Population Reference Bureau. "By 1980, more than 40 percent of mothers with children under 3 years of age were working for pay or seeking such work."

Advocates of affirmative action argue that the inroads made by women in traditionally male jobs are primarily the result of government pressure on employers. But others contend that economics and demand in the labor market play the primary role and that other influences are hard to assess.

"Probably the most difficult thing to quantify over the years is to what extent the changes are traceable to factors such as affirmative action," said Elizabeth Waldman, a senior economist and specialist in women and family issues for the Bureau of Labor Statistics.

"There were so many women coming into the labor force in the 1960s-- and there was a great demand for their work. Without the demand for their work, this whole scenario would not be laid out in front of us. It's hard to disentangle this from women's liberation, affirmative action and all the legislation in this area."

Technological change is another factor. In the occupation of "baker," for instance, the dramatic increase in female practitioners does not signify new armies of women wearing white chef's hats and wielding rolling pins.

"The change has come about mainly because the job of baker has been broken up by mechanization," explained Ronia Garnicki, of the Bakery, Confectionery and Tobacco Workers International Union. "These jobs are more strictly those of machine operators, doing just one aspect of the job over and over, such as making sure the dough goes into a certain pan."

In the past, she added, "when 'baker' was a skilled job, men very jealously held onto the idea of limiting the number of people going through apprenticeship and so forth. Now it's easier to just hire a person off the street and train them."

Now, she said, the job of baker is the kind of job women have always done.

The decline in the rate of work by men reflects, among other things, the impact of more widespread and generous pension, disability and retirement plans, as well as changing social attitudes toward work and the increased workload carried by women, according to analysts in the Census Bureau.

At the same time, male workers have increased in a few fields dominated by women, such as food service workers and nursing. Again the reasons include various social and economic factors.

In the case of nurses, for instance, specialists suggest the increase is partly the result of men coming out of military service in the post-Vietnam era with medical training, in addition to changes in the practice of medicine itself.