It wasn't too long ago that Mexico's government told its young people that the patriotic thing to do was to have large families.
But by the mid-1970s Mexico realized that a country doubling its population every 20 years was never going to get ahead. Result: Latin America's first national family-planning policy and a reduction in population growth that remains an example for much of the developing world.
Yet Mexico today is a country at a demographic crossroads.
Last year the population grew 1.88 percent, compared to 3.5 percent in 1970. But Mexico remains a young country - 40 percent of the population is between 14 and 29 years old. This "bubble" of young people, making decisions on family size over the coming decade, will determine the demographic road Mexico takes.
Mexico is not alone. Of the world's 6 billion people, more than 1 billion are adolescents who will make reproductive decisions over the coming decade, as Hillary Rodham Clinton noted at the UN's population and development forum last week in The Hague. These decisions, demographers emphasize, will have a profound effect on the world's environmental, social, and economic future.
In Mexico young people confirm that, in the cities, the rule of small families is already well established. Take Csar Guarnel and Dolores Gmez, both pharmacology students in Mexico City. They giggle when asked if they plan to marry each other some day, but they are both sure that no matter whom they marry, they want no more than two children.
"With fewer children you have a much better chance to provide for them, and I mean by that the things they need: a good education, a decent home, even nutritious foods," she says.
She and Mr. Guarnel say all their friends think "small" when the subject is family size. But they also agree that the challenge for Mexico is not so much in the country's main cities but in the rural areas where women still have significantly more children than the national average.
Adds Jaime Ocampo Hernndez, a young Mexico City industrial engineer: "The key to success is in rural zones, because people are marginalized there. They don't get the information and the assistance - and the logical result is that that's where population growth remains the highest." Some 80 percent of births in Mexico today occur within the poorest 20 percent of the population, officials say. And the greatest concentration of those births and that poverty is in rural areas.
Mexico has taken internationally recognized steps to correct the lack of reproductive planning services in rural areas, and the government has also moved to tie participation in antipoverty programs to family-planning practices.
But tight fiscal management and falling international oil prices - with their direct effect on this oil-producing country's budget - have led the government to reduce spending on family-planning programs.
The government is seeking to make family planning more than simply a women's issue by including reproductive education and family planning in all levels of public education.
But the program is controversial, colliding with the position of the Roman Catholic Church and conservative family groups who insist the topic should be treated by parents in the home.
And even supporters of the school program say it cannot be considered enough, since many adolescents - especially girls in rural areas - are no longer in school when information most pertinent to their age is offered at the secondary level.
With Mexico's demographic future in the balance, some proponents of more extensive family-life education for adolescents also worry that next year's national elections could set back their cause.
Guanajuato Gov. Vicente Fox, member of the opposition National Action Party (PAN), is the leading presidential candidate according to very early polls. But the center-right PAN is considered the closest of Mexico's major political parties to the Catholic Church, and PAN elected officials have a history of promoting conservative social agendas.