Parents who decide to have only one child in Jilin Province in China receive annual wage bonuses of 50 yuan - 7 percent of average rural income - until the child is 15.
They also get a private plot of land twice as big as usual, an adult rice allowance for the child, and low-cost health care.
Indonesian families with no more than two children are eligible for special education scholarships. They also receive seeds of a valuable hybrid palm tree.
When men and women in a poor fishing village near Colombo, Sri Lanka, agree to plan their families, they can get between five and ten six-month-old chickens free of charge and sell the eggs.
Thirty African, Asian, and Latin American countries are testing programs such as these to find out if incentives in cash or kind can help lower their population growth rates.
But do such incentives actually work? Or in very poor societies, do they represent a form of coercion which encourages abortion and sterilization?
These questions are among a number of underlying issues being debated by delegates from 140 countries attending the Second World Population Conference here in Mexico City Aug. 6 to 13.
Opinions are divided, within the third world itself as well as in nations such as the United States that provide aid funds for family planning.
''Incentives reinforce decisions already made,'' says a New Delhi social worker. ''They help push couples who have made the decision to adopt contraception to go to a clinic and actually start.''
''We don't call our government payments 'incentives' at all,'' says Dr. Wickrema Weerasooria, a senior adviser to Sri Lanka's President. ''We regard them as compensation for the time a woman - or man - has to take in leaving home and job and coming in to family planning clinics.''
In 1981 the Sri Lankan government began offering payments of 100 rupees to men and women who agreed to sterilization. When privately owned tea plantations began paying employees up to 700 rupees, the government raised its own payments to 500.
Right-to-life, anti-family-planning groups in Washington persuaded the Reagan administration to withhold US aid funds as a result.
''But we continued the payments anyway,'' Mr. Weerasooria said, ''and now US aid funds have been reinstated.''
A critic of such payments is Dr. Lessel David, senior health and population consultant at the prestigious Administrative Staff College in Hyderabad, India.
In a recent interview Dr. David argued that people simply don't decide to have fewer children because such decisions produce a one-time financial payment.
''They decide for many other reasons,'' he said. ''They want to give the children they have better opportunities, or they just can't afford to have another....''
Dr. David raised one point often made by critics: Cash incentives can lead to fraud and corruption.
In Sri Lanka, a woman seeking sterilization must be under age 45 and already have two children. The youngest must be 12 months old. ''We have had cases of bogus age certificates,'' says a voluntary group organizer, ''and of young people saying they have two children when they do not.''
The World Bank Development Report for 1984 warns that incentive and disincentive programs (limiting tax benefits for families containing more than a specified number of children) ''require extra care to avoid unfairness and abuse....
''When payments are offered as an inducement to sterilization,... care must be taken that the poor are not being tempted to act out of short-term economic necessity contrary to their long-term interests.''
Incentives in China vary because they are adopted by local rather than national authorities. Many one-child families receive red and gold ''glory cards'' entitling them to extra benefits. Among disincentives: A family can lose 15 percent of its income if a second child is born, and another 10 percent for a third child.
Critics see China's one-child-per-family policy as coercive. But the leader of the Chinese delegation to the Mexico City conference, Family Planning Minister Wang Wei, said the policy was flexible and widely supported.
Singapore and South Korea also have nationwide policies to reward couples who limit family size and to punish those who don't financially.
Singapore limits tax relief above three children, restricts paid maternity leave to the first two pregnancies, and allocates state housing as if every family had two children. Larger families are more cramped.
A new and controversial policy retains incentives for poorer families to have only one or two children and encourages women university graduates to have larger families.
The World Bank reports that in Ghana, Malaysia, Pakistan, and the Philippines tax deductions, child allowances, and maternity benefits are also geared to smaller families. In Tanzania a woman is eligible for maternity leave only once every three years.
Indian states are starting to introduce incentives similar to those in China.