51吃瓜

For nearly seven decades, the UN has been collecting and analysing population data from countries or areas around the world to estimate the number of humans inhabiting planet Earth today and in the future. What do these numbers tell us? And why is it so important to be counted? As UN DESA prepares to launch the 2019 revision of World Population Prospects on 17 June 2019, we ask Thomas Spoorenberg, Population Affairs Officer at UN DESA’s Population Division.

World Population Prospects is considered the most accurate and trusted estimate of the human population. How is it produced?

“The UN Population Division, which is part of UN DESA, has been estimating and projecting the world’s population since 1951. A team of more than a dozen people has worked for more than a year on this latest update. We have spent most of our time analysing recent trends in fertility, mortality and international migration to determine the size and age structure of the population for 235 countries or areas.”

Where do all these data come from?

“We evaluate population censuses, vital registration of births and deaths and household surveys. For example, this latest assessment considers the results of 1,690 population censuses conducted between 1950 and 2018, information on births and deaths from numerous vital registration systems and demographic indicators from 2,700 surveys. We then feed those estimates into statistical models to project the future trajectories of fertility and mortality that will determine, in conjunction with future international migration, the future population of each country or area through 2100 and to assess the certainty of those projections.”

Going beyond the numbers, this publication talks about billions of real people – where they live, how old they are, whether they migrate. Why is it important to know all these things?

“Understanding global population trends and anticipating the demographic changes to come are crucial to sustainable development. The population trends we are observing over the past few decades tell us that we have made substantial progress towards several of the Sustainable Development Goals (SDGs), such as reducing mortality among children, increasing access to sexual and reproductive health care and enhancing gender equality to empower women to decide freely and responsibly on the number of their children.

Looking ahead, by the year 2030, our population will be different from what we see today, and it will change even further by 2050. Societies need to adapt by anticipating future demographic trends and incorporating that information into policy and planning. For example, countries with rapid population growth, mostly in sub-Saharan Africa, must plan to provide schooling and health care to growing numbers of children and ensure education and employment opportunities to increasing numbers of youth. Countries where the population has already ceased, or will soon cease, to grow must prepare for an increasing proportion of older persons and, in some cases, decreasing population numbers. With long-term objectives, such as the SDGs, analyzing population trends help us to plan not only for today’s, but also for tomorrow’s population.”

One thing we know already, even before the launch of the latest revision, is that our population is growing. Can we achieve the SDGs and curb climate change with even more of us on this planet?

“It’s true that the global population continues to grow, but the rate of increase is slower today than at any time since 1950 and we expect it to continue to slow over the coming decades. Overall, the world has been rather successful in reducing poverty and increasing the quality of life for many of the more than 5 billion people added to our population since 1950. But the world’s economy will need to grow sustainably to support the growing global population and to avoid negative impacts on the environment. Many of the fastest growing populations are in the world’s poorest countries. In these countries, population growth is a real challenge for efforts to eradicate poverty and inequality, combat hunger and malnutrition, strengthen the coverage and quality of education and health systems, and improve access to basic services.

Having said that, we should remember that population size and growth is just one part of a complex sustainable development equation, which also includes issues such as consumption, technology and the state of the environment. Slower population growth can help achieve the SDGs and the Paris Agreement climate targets, but it is even more important to encourage more responsible patterns of consumption and production that can ease pressure on ecosystems to generate food, preserve natural resources and allow the world more time to identify and adopt new technologies.”

Our population is not only getting larger, it is increasingly getting older. What will an older world look like? What adjustments will we have to make?

“Persons aged 65 or over already make up the world’s fastest growing age group and virtually all countries can expect the percentage of older persons in their populations to increase. Countries need to plan now for population ageing to ensure the well-being of older persons, the protection of their human rights, their economic security, access to appropriate health services and lifelong learning opportunities, and formal and informal support networks.”

For more information:

Watch the launch of the 2019 Revision of the World Population Prospects live on 17 June, at 12 noon EDT on