The world is due to reach 8 billion people today, November 15! This very precise date hides an uncomfortable truth – we don’t really know exactly how many people there are in the world. This is especially true in lower-income countries; those where population growth is increasingly concentrated. While these milestones such as reaching 8 billion people are important in raising public awareness of population issues - such as unmet needs for family planning or changing population-age-structures - they can give a somewhat misleading impression of the certainty of our knowledge on population.
The population in Asia and the Pacific reached 4.67 billion in 2021, accounting for 59 per cent of the world’s population. The region is projected to be home to 5.17 billion people by 2050. But for both the regional and global population, there is actually a large degree of uncertainty over the exact number.
So how do we know when the world will reach 8 billion?
The day on which the world reaches 8 billion is determined by experts in the Population Division of the United Nations Department of Economic and Social Affairs and is based on estimates and projections for each country.
In order to determine the population size, we need to know the population at a particular point in time and consider changes as a result of births, deaths and cross-border migration, with migration being the most difficult to estimate.
The figure of 8 billion for the global population comes from the aggregation of the populations of all countries and areas of the world. Every two years, the Population Division releases a set of revised and updated population estimates, the World Population Prospects, starting from 1950 to 2021, and projections, from 2022 to 2100, for all the 237 countries and areas of the world. The population of each country or area is calculated by applying separately trends and levels of births by sex, and deaths and migration for each age and sex group of the known population of a specific earlier year. The national population is then projected forward by age and sex to come up with an estimate or a projection for each year, disaggregated by age and sex.
However, the production of quality population estimates and projections is dependent on the collection of reliable and timely demographic data from civil registration and vital statistics systems, population censuses, population registers and household sample surveys. Even today, in 2022, this collection of basic demographic information remains a challenge.
Many countries in Asia and the Pacific are far from achieving universal registration of births and deaths, which means they use surveys and censuses to calculate vital statistics and population estimates. While these sources can provide very important data of the situation at a particular time, they cannot provide continuous and timely data. The preferred source of vital statistics is a comprehensive civil registration system that collects information soon after the birth or death occurs. Because civil registration should be compulsory and universal, the resulting vital statistics are comprehensive and accurate and not subject to response or sampling errors that arise when vital statistics are estimated using household surveys or censuses.
An additional challenge is presented by the lack of census data and other survey data. Some countries have not conducted a population census in decades, while many countries postponed the most recent census due to the COVID-19 pandemic. For example, the census of India, accounting for some one-sixth of humanity, was delayed to 2023.
Will we know when we reach 9 billion?
Current projections suggest that we will reach 9 billion people in 15 years. We hope that by then we will have significantly improved the quality and availability of population data. We probably still won’t know the exact date but countries, the UN and development partners are working to make sure that we can determine it more accurately than we can now.
One example is how, in recognition of the importance of CRVS systems, governments in Asia and the Pacific are collectively working to achieve their common goals as listed in the Ministerial Declarations to "Get Every One in the Picture" and “Building a More Resilient Future with Inclusive Civil Registration and Vital Statistics”. Accordingly, participating governments developed the Regional Action Framework on CRVS in Asia and the Pacific, which includes goals on universal birth and death registration and the production and dissemination of accurate, complete and timely statistics, including basic population estimates. We have seen progress since the beginning of the Decade and we hope to accelerate it. Another example is work to improve the use of administrative data for censuses in the region.
Countries have also committed to improving data collection in the Ministerial Declaration of the Sixth Asia-Pacific Population and Development and ESCAP supports endeavours in that regard. Furthermore, the Population Division works to strengthen national capacities to estimate and analyse population levels and trends and other demographic indicators.
With these efforts and many more to come, we will hopefully be able to say with a bit more certainty when we really do reach 9 billion.