WHILE much of the rhetoric in Cairo this week has centered on abortion and traditional values, the bottom line is money.
Like venture capitalists on the social front, delegates from 177 countries at the United Nations International Conference on Population and Development will debate funding for a highly successful enterprise: international family planning. But these investors define success differently from most. They want world population to stabilize at about 7.8 billion by 2050.
''Money is the transcendent issue at Cairo,'' says Joseph Speidel, president of the Washington-based Population Action International, a nonprofit research organization.
How much money is needed? Some $22 billion a year by 2015, says a PAI report released today entitled ''Financing the Future: Meeting the Demand for Family Planning.''
''If you think that sounds like a lot,'' says Shanti Conly, PAI's director of research, ''consider that last year Americans spent $33 billion to get thin.''
The movement's successes would encourage any investor. In the developing world, the average number of children per family has dropped from six to four in the past three decades - not quite halfway to the 2.1 needed for population stabilization.
DESPITE this success, the World Health Organization estimates that 40 percent of women in the developing world have no ''easy access'' to family planning: They have to spend more than 1 percent of their yearly income and travel more than 2 hours to obtain family-planning services.
If the world's family-planning effort were a car, Dr. Speidel says, ''We currently have a model with two wheels off.'' And although PAI says $17 billion would provide enough services for now, it also projects a rise in costs to $22 billion by 2015.
This expected increase stems from a growing population and an effort to broaden the range of contraceptives, prevent sexually transmitted diseases, and give better reproductive health care. Every nation will have to spend more to reach these goals, and developing nations shoulder much of the burden. But PAI recommends that developed countries raise family-planning expenditures from 25 to 33 percent of the worldwide total.
The United States has already increased its family-planning aid from $310 million to $595 million for 1995; the PAI report calls for $1.8 billion by 2000, and $2.3 billion by 2015.
The prospect of reaching world-wide spending targets is tenuous. ''It's all a matter of the political will generated in Cairo,'' Ms. Conli says.