The increase in the past few years in the number of working women -- and working mothers -- has been well documented. Nearly half of the mothers of preschool children are now in the work force, which itself is 43.3% female.

The past four years have seen an increase in the number of U.S. employers offering child-care services and support for the children of those women as well, from about 100 in 1978 to more than 500. Surprisingly, however, recent research shows that the conventional explanations for why companies begin a day-care program -- tax incentives and cost controls -- aren't what persuade top executives.

Instead, according to Renee Magid, a professor of education at Beaver College in Glenside, Pa., "better personnel relations" and "social consciousness and awareness" are among the most common explanations for instituting day care. Magid surveyed some 600 companies and hospitals offering child-care benefits. "Employers don't initially get involved because of cost-control issues," she says. "I think they get involved because a CEO has four daughters at home, or somebody comes to him and does a real heavy number in terms of education, and then they find out on down the line all the other things."

Magid was particularly surprised by the importance of "social consciousness" to top executives. "That is something that maybe we haven't thought about management before," she says. Ninety percent of the employers responding said that the benefits of child care outweigh the costs. While the economic downturn has led to major cuts in many employee benefits, almost none of the companies plans to cut back its child-care initiatives.

The increasing interest in employer-sponsored child care has led to the creation of an unusual new service by Jean Bruce, 55, of Norfolk, Va., who calls herself America's first day-care "broker." Bruce organized some 100 providers of family day care -- each permitted to care for up to nine children -- into a network of day-care providers. She then visited companies in the Tidewater area to market membership in her network. An employee of any company that joined received a 20% discount off the $50 membership fee. Ten companies have joined so far, including four major banks, three hospitals, and an insurance company. Annual corporate fees range from $250 to $2,000, depending on the number of female employees under the age of 50 in each company. Clients also agree to "endorse" the plan and to allow Bruce to hold educational meetings for employees.

"I think you have to appeal to employers on the basis of common sense and compassion," Bruce says. She first described her service to prospective clients as a fringe benefit for employees, "but that didn't seem to elicit a very warm response." Instead she began stressing that good child care is "a genuine need for employees," a way to encourage regular attendance and better attention to the job. Like Professor Magid, Bruce has discovered that social concern is a primary motivation for a company's involvement in day care. "What I have to offer helps employers respond to a genuine interest on the part of their employees," she says. And it sells.