In 1968, Paul Ehrlich published his bestseller The Population Bomb, which warned that worldwide overpopulation would cause mass starvation and societal upheavals in the future. This book was indicative of the widespread fear of a “population explosion” in the 1950s and 1960s, which was predicted to strain the planet’s resources and cause global food shortages, among other catastrophic events. Since then, however, some parts of the world have been debating about not overpopulation, but underpopulation.

On April 8, The New York Times reported that Denmark was undertaking several initiatives to solve its underpopulation crisis and the issue of its low birth rate. One such initiative entails adjusting its sex education program to talk to teenagers about pregnancy in a more positive light, while still educating them on how to avoid getting pregnant. Marianne Lomholt, the director of Sex and Society, said, “For many, many years, we only talked about safe sex, how to prevent getting pregnant … Suddenly we just thought, maybe we should actually also tell them about how to get pregnant.”

Denmark and other European countries have long suffered from a low birth rate that is below the widely accepted 2.1 children per woman necessary to maintain a population at its current size. In other words, unless these countries can reverse the decline of their birth rates, their native populations will continue to shrink in size. Furthermore, as each generation is filled with fewer people, the number of elderly people for every one young person will continue to increase, putting a burden on social pension systems and requiring heightened elderly care.

As a result, the governments of these countries have become increasingly anxious about underpopulation. Germany’s former Minister of Defense, Ursula von der Leyen, declared that if Germany didn’t turn its declining birth rate around, it would have to soon “turn out the light.” Meanwhile, André Rouvoet, leader of the Christian Union Party in the Netherlands, has strongly urged the government to encourage people to have more children.

To combat the threat of underpopulation, these countries have made a variety of plans and attempts to encourage people to have more children. These plans range from making child rearing easier for families through measures such as family subsidies, to encouraging people to have children by offering financial incentives, to promoting childbirth with ideas linking child birth to patriotic duty.

Spies, another Denmark-based organization in the travel industry, launched an initiative last year that aired several commercials showing a young Danish couple booking a hotel in Paris to do their duty of raising their nation’s birth rate.

Given historical attempts to raise national birth rates in the past, these measures should be met with skepticism. In 1944, the Soviet Union began bestowing the honorary title of “Mother Heroine” upon women who were raising 10 or more children. Over the next few decades, more birth rate-centered policies were passed, such as increased benefits for families with children and lump-sum payments for giving birth to a child. By 1981, the Politburo offered a year of partially paid leave for women who had a baby. Then, in 1986, it increased this to a year and a half.

But despite these attempts to resolve underpopulation in the late 20th century, the Soviet Union’s fertility rate declined in the 1950s, 1960s and 1970s, with the exception of a short increase in the late 1980s, after which it declined again. Measures taken by other countries in the past have been met with equal numbers of success and failure, which suggests that the birth rate might be somewhat out of a government’s control. Population studies scientist Jan Hoem supports this, saying that fertility is “best seen as a systemic outcome that depends more on broader attributes, such as the degree of family-friendliness of a society, and less on the presence and detailed construction of monetary benefits.”

Perhaps European countries with low birth rates should see if they can find a way to more effectively control the social norms on having children, before they start handing out cash incentives.