The world welcomed its 7 billionth inhabitant today when tiny Danica May Camacho made her appearance in a Manila, Philippines, hospital to great fanfare. India also greeted its version of the 7 billionth person on earth: a girl named Nargis, born in the state of Uttar Pradesh.

That these two symbols of a major population milestone were girls is only a coincidence, but it is also a reminder that central to global progress in stabilizing population growth has been the empowerment of women and greater gender parity. Given greater opportunities and rights, women make decisions that slow population growth, and this impact is being seen worldwide, says Babatunde Osotimehin, the executive director of the United Nations Population Fund.

"The move from the 1960s, when the population was 3 billion, to the currently predicted 7 billion," notes Paul Demeny, a distinguished scholar at the New York-based Population Council, "well, that happened in, what – half a century? It will not happen again at that scale. There is every possibility [for the] global economy to cope with this [latest] addition."

It took only a dozen years to make the leap from 6 billion. And according to the same projections found in this year's State of the World Population report from the UNFPA, the population will top 9 billion by 2050 and 10 billion by the end of this century.

Of course, the United Nations' pinpointing of Oct. 31 as the day the world population tops 7 billion is an imprecise choice, as the date was based on mere projections. The 7 billionth inhabitant could have been born months ago, or could still be in the womb.

While the numbers may be staggering, the report paints a far less Malthusian picture than has been bandied about in recent years.

Rate of growth has slowed since '60s

Total population is still climbing, but the rate of growth peaked in the 1960s at about 2 percent. It has steadily declined since then, although it remains well above replacement level in places like sub-Saharan Africa, where it still tops 2 percent.

Stabilizing fertility rates – the average number of children born to a woman in her lifetime – is key to managing population growth. The starting point: more education for girls. That can start a "virtuous cycle" of delayed marriage and childbearing, which leads to fewer children and more investment in the children that are born, says Judith Bruce, a senior associate and policy analyst at the Population Council.

If a girl in the developing world spends just a few more years in school, she has more bargaining power in the home when she does marry. When girls and young women have a say, they tend to have fewer children, and those children stay in school longer, Ms. Bruce says.

Education "has a tremendous return [in] all the things that change family size and improve the distribution of resources," Bruce says. "A woman who educates her children sets in process reduced fertility" – fewer, better-cared-for children.

Of the Millennium Development Goals set forth by the UN in 2000, expanding education for women is the one where the world has made the most progress, Mr. Osotimehin says. A high school education is now widely accepted as the minimum a girl should have.

If marriage and childbearing are delayed just five years in the least developed countries, until after adolescence, this would lead to 224 million fewer children born by 2050, according to Population Council data. That would represent a 39 percent reduction in how much the UN expects the population to increase by 2050.

Modernization also plays a critical role. A glimpse of better living options typically spurs people to improve their lot in life. The effect of this is evident in Western Europe, where population growth is at a virtual standstill, Mr. Demeny says.

People rapidly adjust their plans for large families as they realize that children are expensive to raise.

"The basic pressure of conflict between striving for a better standard of living and raising four, five, six children will result in a natural adjustment in fertility rates," Demeny says.

Among city dwellers, particularly couples who are better educated, the average number of children drops by a considerable margin, he says. With more than half the world now living in cities, according to the UN report, that trend has considerable implications for easing population growth.

Challenge to planet's resources

But even if fertility rates begin declining more rapidly, population growth is "certain" because of the vast number of young people who are entering their childbearing years, says Jose Miguel Guzman, chief of the population and development branch at UNFPA. According to the UN report, people under the age of 24 make up 43 percent of the world population today, and, according to Mr. Guzman, almost 48 percent of the population in developing countries.

The proportion of young people in developing countries is likely to continue increasing at least until 2050, he says. The biggest challenge posed by the boom in the youth population – which, according to Guzman, will not stabilize until 2100, at about 30 percent of the world population – will be to ensure that young people have sufficient economic and educational opportunities, Osotimehin says.

Concerns about supplies of food and energy have raised questions of whether the Earth is approaching its carrying capacity – the number of humans it can support.

The good news? Human ingenuity – technological advances, enlightened government policies – have a significant impact.

"With the population we have, we've already experienced some pressure," Guzman says. But "what happens in the future depends on the action we take today."