Population change – Outlook from UN DESA

Assessment versions

Published (reviewed and quality assured)

• No published assessments

Rationale

Justification for indicator selection

Trends in the size and structure of human population play a key role in the environmental impact of countries and regions (UN, 2013a). Demographic trends strongly influence economic activities, which in turn determine demands on ecosystems and levels of pollution (UNFPA, 2012).  Consequently, trends in population size and structure may provide an indication of likely pressures on natural resources, such as freshwater abstraction, land use, soil degradation, resource use, landscape fragmentation and pollution.

Population size and structure also influence the consumption patterns and resilience of communities. For example, the current trend across Europe and some other developed regions towards an 'ageing society' may increase the vulnerability of society to adverse environmental change (e.g. climate change) and new patterns of disease (EEA, 2014b).

Migration, which is a major determinant of population change, can be a response to changing environmental, social or economic circumstances or a cause of such changes (ICMPD, 2011; EEA, 2014a). Understanding possible changes in migration patterns between countries is crucial for forward planning of potential demand on countries’ infrastructure – including natural capital, health and education (IOM, 2009).

This indicator may help decision makers to understand potential demographic trends for Europe and other world regions, thus assisting in the development of sustainable development policies and measures.

Scientific references

• EEA, 2014a, Assessment of global megatrends – an update. Global megatrend 1: Diverging global population trends EEA, Copenhagen, Denmark
• EEA, 2014b, Assessment of global megatrends – an update. Global megatrend 3: Changing disease burdens and risks of pandemics EEA, Copenhagen, Denmark
• ICMPD, 2011, ‘Climate refugees’ – Legal and policy responses to environmentally induced migration Report for the European Parliament’s Committee on Civil Liberties, Justice and Home Affairs, International Centre for Migration Policy Development
• IOM, 2009, Migration, environment and climate change: Assessing the evidence International Organization for Migration, Geneva, Switzerland
• UN, 2013, Population, development and the environment 2013 United Nations Department of Economic and Social Affairs (UN DESA), New York, US.
• UNFPA, 2012, Population matters for sustainable development United Nations Population Fund.

Indicator definition

Population includes all residents regardless of legal status and citizenship.

Population change is defined as the “population increment over a period, that is, the difference between the population at the end of the period and that at the beginning of the period. It refers to five-year periods running from 1 July to 30 June of the initial and final years” (UN, 2013c). Within this indicator this includes natural population change (the difference between the number of live births and deaths during a given time period) (Eurostat, 2015) and net migration (the difference between the number of persons entering and leaving a country during a given period) (UN, 2013c).

The figures presented in this indicator include historical data and eight projection variants. These projection variants have been developed by UN DESA on the basis of varying assumptions related to fertility rates, mortality rates and international migration (for details see the Methodology section). The table below summarises the eight projections variants as defined in the World Population Prospects: The 2012 Revision(UN, 2013d).

Assumptions

Time horizon: 1950 to 2100

Geographical coverage: global, with specific attention to world regions and Europe. World regions are specified as defined by the United Nations Population Division Department of Economic and Social Affairs: Asia; Africa; Europe; Latin America and the Caribbean; Northern America; Oceania.

References

Eurostat, 2015, 'Glossary: Natural population change'

UN, 2013c, 'World Population Prospects: The 2012 Revision — Glossary of demographic terms'

UN, 2013d, 'World Population Prospects: The 2012 Revision — Highlights and advance tables', Working Paper No. ESA/P/WP.228, United Nations Department of Economic and Social Affairs (UN DESA), New York, US.

Units

Number of people; percentage of people

Policy context and targets

Context description

Global policies

Although population is not subject to direct international policy it is recognised that population growth is central to many policy issues that the international community seeks to address. International organisations have put in place policies, programmes and funding to provide greater awareness and choice about birth control and demographic change. Examples include the United Nations Population Fund (UNFPA) which aims to “[deliver] a world where every pregnancy is wanted, every birth is safe, and every young person's potential is fulfilled” (UNFPA, 2015).

European Policies

There are no EU policies directly regulating Europe’s population size and structure. There are, however, a number of relevant initiatives. For example, in light of the on-going demographic changes in Europe (such as an ageing population, low fertility rates, changing family structures and migration) the European Commission issued a Communication "The demographic future of Europe – From challenge to opportunity" (COM(2006) 571 - final), which identified five key policy responses to manage demographic change

1. Supporting demographic renewal through better conditions for families and improved reconciliation of working and family life
2. Boosting employment – more jobs and longer working lives of better quality
3. Raising productivity and economic performance through investing in education and research
4. Receiving and integrating migrants into Europe
5. Ensuring sustainable public finances to guarantee adequate pensions, health care and long-term care.

This strategy was renewed in 2009 with a new Communication “dealing with the impact of an ageing population in the EU” (COM(2009) 180 final). Aspects of this were included in Europe 2020, the European Commission’s growth strategy (COM(2010) 2020 final). One example of the Europe 2020 umbrella activities aimed at addressing European demographic trends is the Ambient Assisted Living Joint Programme (AAL JP), intended to support industry in providing services and products for an ageing population (EC, 2013).

Furthermore, the European Demography Forum, held by the European Commission every two years since 2006, provides policymakers, stakeholders and experts opportunities for knowledge sharing and discussion around demographic change. 

In 2014 the European Commission issued a five point-plan on immigration including measures to secure Europe’s borders and to control and facilitate asylum and legal migration (EC, 2014). It recognises the need to develop a common legal migrati­on policy to meet the increasing demand for skills and talents likely to arise as a result of the forecast demographic trends in the EU by 2060.

At the national and European regional level, additional initiatives and policies exist to address the specific demographic challenges.

Targets

There are no global, pan-European or EU objectives and targets relating to population.

Related policy documents

• COM(2006) 571 final - The demographic future of Europe – From challenge to opportunity
  (EC, 2006)
• COM(2009) 180 final - Dealing with the impact of an ageing population in the EU (2009 Ageing Report)
  For the first time in history, the vast majority of Europe's citizens are able to lead active, healthy and participative lives well into old age. At the same time, ageing societies bring new opportunities to innovative firms through the demand for new or adapted goods and services.However, the combination of ageing and low birth rates also poses major economic, budgetary and social challenges.
• COM(2010) 2020 final, Europe 2020: A strategy for smart, sustainable and inclusive growth
  European Commission, 2010. Europe 2020: A strategy for smart, sustainable and inclusive growth. COM(2010) 2020 final. 
• EC, 2013 - Tackling the demographic challenge
  Tackling the demographic challenge to create growth and jobs - Commission proposal for a renewed Ambient Assisted Living Joint Programme (AAL JP)' (ec.europa.eu//digital-agenda/en/news/tackling-demographic-challenge-create-growth-and-jobs-commission-proposal-renewed-ambient) accessed 23 January 2015.

Methodology

Methodology for indicator calculation

Methodology for indicator calculation (i.e. generating projections until 2100)

The United Nations World Population Prospects (WPPs) are produced every two years. The 2012 version, presented here, was published in 2013 (UN, 2013).

The data set includes recorded (historical) data covering the period 1950–2010 and Outlook data (projections) for the period 2010–2100. The creation of both aspects of the data involves numerous methods and assumptions.

Since the 2010 revision the Population Division has developed further the methodology for producing probabilistic projections for all countries and areas of the world. In the 2010 Revision this was limited to fertility but the 2012 Revision incorporates, for the first time, probabilistic projections of mortality (UN, 2014).

Historical data

Past estimates of demographic variables are taken either directly from national statistical offices, or estimated by staff within the United Nations on the basis of the best available national or international estimates at the time. These population estimates are based on the most recently available data sources.

The five main recorded data sources (Heilig et al., 2012) are:

• Census data (and post-enumeration surveys).
• Demographic and health surveys.
• Estimates from population and vital registers.
• Scientific reports and data collections.
• Data estimates provided by international agencies (e.g. EUROSTAT, WHO).

In some cases, it is deemed necessary to adjust the original data if there are identified deficiencies in age reporting, under-enumeration, or under-reporting. Adjustments are also made to take account of international migration flows (UN, 2014). These adjustments are made as more data become available, supported by expert review and assessment.

Projection variants

Predicting the structure and trajectory of future populations is based primarily on an understanding of the extant population and the fertility rate.

The extant population is based on the data sources set out previously.

Fertility rate calculations are based on four sources: vital registers (which report the number of births and age of the mother); surveys (of countries without vital registers); census; and adjustments (revised historical data).

Other key factors that are used to predict future populations are mortality and migration. For these factors the 2012 revision includes a new probabilistic method, which includes two separate steps: understanding progress made in female life expectancy at birth, and the gap between female and male life expectancy at birth.

As with the fertility models the results of this approach produce country-specific projections of life expectancy at birth that are fully reproducible and take into account past empirical trends. For some countries, those with exceptional changes in mortality, expert judgement is applied to the models to sense-check the results.

Data on international migration is recognised by the United Nations as being inadequate in the majority of countries. In these instances international migration is calculated, in part, on the basis of the difference between the actual recorded population change and the independent estimates of natural increase (i.e. a calculation of population change based on estimates of fertility and mortality).

Assumptions for projection variants

The following assumptions and combinations thereof have been used to generate the eight projection variants of the 2012 revision of the WPPs (UN, 2013d, with relevant page):

• Medium fertility – “Assumes that 184 countries will reach below-replacement fertility by 2095 – 2100 and more than 81 per cent of the world’s population will be living in a country where the average number of children per woman will be below 2.1” (p.11)

• High fertility – “Under the high variant, fertility is projected to remain 0.5 children above the fertility in the medium variant over most of the projection period. By 2020-2025, fertility in the high variant is therefore half a child higher than that of the medium variant. That is, countries reaching a total fertility of 2.1 children per woman in the medium variant have a total fertility of 2.6 children per woman in the high variant” (p.35)

• Low Fertility – “Under the low variant, fertility is projected to remain 0.5 children below the fertility in the medium variant over most of the projection period. By 2020-2025, fertility in the low variant is therefore half a child lower than that of the medium variant. That is, countries reaching a total fertility of 2.1 children per woman in the medium variant have a total fertility of 1.6 children per woman in the low variant”. (p.35)

• No-change – fertility and mortality are assumed to be constant as of 2005 – 2010 and international migration is ‘normal’.

• Constant fertility – “For each country, fertility remains constant at the level estimated for 2005-2010”. (p.35)

• Instant replacement – “For each country, fertility is set to the level necessary to ensure a net reproduction rate of 1 starting in 2010-2015. Fertility varies over the rest of the projection period in such a way that the net reproduction rate always remains equal to unity thus ensuring, over the long-run, the replacement of the population”. (p.35)

• Zero migration – “Under this assumption, for each country, international migration is set to zero starting in 2010-2015”. (p.46)

• Normal mortality – “For countries with recent empirical information on the age patterns of mortality, mortality rates for the projection period were obtained by extrapolating the most recent set of mortality rates by the rates of change from either (a) country-specific historical trends upon availability, reliability and consistency over time using an extended Lee-Carter approach, or (b) typical age-specific patterns of mortality improvement by level of mortality estimated from individual countries experiences included in the Human Mortality Database, or from extended model life tables.” (p.44)

• Constant mortality – “Under this assumption, mortality over the projection period is maintained constant for each country at the level estimated for 2005-2010.” (p.46)

Methodology for gap filling

Past population trends are based on estimates for 233 countries and areas. Approximately half of those countries or areas do not report official demographic statistics with the detail necessary for the preparation of cohort-component population projections. The United Nations Population Division undertakes its estimation work in order to fill those gaps.

One way this is achieved is via major survey programs, such as the Demographic and Health Surveys or the Multiple-Indicator Cluster Surveys (which are a series of United Nations supported house-hold surveys) (UNICEF, 2013).  These are used to generate some of the data that are not currently provided by official statistics.

The analysis carried out by the United Nations Population Division takes into account the data gaps and seeks to establish past population trends by resolving the inconsistencies affecting the basic data. This is achieved by grouping and comparing relevant countries and then extrapolating trends.

Methodology references

• Heilig et al., 2012 Population estimates and projections section: Work program, outputs, challenges, uncertainties. Heilig, G. K., Gerland, P., Andreev, K., Danan Gu, N. L., Spoorenberg, T., Ravinuthala, S., Yamarthy, C. and Koshy, N., 2012, United Nations Department of Economic and Social Affairs (UN DESA), New York, US.
• UN, 2013b World population prospects: The 2012 revision, United Nations Department of Economic and Social Affairs, New York, US.
• UN, 2013c World Population Prospects: The 2012 Revision — Glossary of demographic terms
• UN, 2013d World Population Prospects: The 2012 Revision — Highlights and advance tables, Working Paper No. ESA/P/WP.228, United Nations Department of Economic and Social Affairs (UN DESA), New York, US.
• UN, 2014 World Population Prospects: The 2012 Revision — Methodology of the United Nations population estimates and projections, Working Paper No. ESA/P/WP.235, United Nations Department of Economic and Social Affairs (UN DESA), New York, US.
• UNICEF, 2013 Multiple Indicator Cluster Survey (MICS)

Data specifications

EEA data references

• No datasets have been specified here.

External data references

• UN world population prospects: The 2012 revision

Data sources in latest figures

Uncertainties

Methodology uncertainty

Identified uncertainty in the United Nation’s forecasts includes changes to future fertility rates, in particular second generation fertility (i.e. the fertility of current mothers’ children), child mortality, life expectancy and migration.

The forecasts use a Bayesian Hierarchical Model (BHM), which produces country-specific distributions for these uncertainties. These distributions are informed by the countries’ historical trends and the observed variability in historical trends for all countries. This means that within the model countries are grouped into different categories based on historical mortality and fertility trends. For example, for countries that currently already have a high life expectancy, smaller increases in life expectancy are predicted than for countries with currently comparatively low life expectancy (UN, 2014) (p.28). Likewise, countries with high levels of HIV/AIDS use slightly different models to account for the impact of this disease (UN, 2014) (p.35).

Historical trends are also used to model fertility trajectories over time, using three differing categories: high; medium; and low. These categories are based on historical evidence that suggests there is a transition over time as countries move from high, to low fertility and that it is possible to forecast fertility using historical data and trends. However, this approach is linked to uncertainties, in particular with respect to the development of fertility after the low fertility phase.

The United Nations recognise that migration is the most challenging feature to predict. In estimating migration the United Nations takes into account four pieces of information: (1) net international migration as recorded by countries; (2) data on labour migration flows; (3) estimates of undocumented/irregular migration; (4) and data on refugee movements in recent periods.

Most migration forecasts are based on the assumption that recent levels, if stable, would continue up to 2050. The countries are asked to provide expert views on international migration as well as estimates of undocumented and irregular migration flows affecting a country. It is also assumed that refugees return to their country of origin within five to ten years. Where a country has experienced both international migration and refugee movements, the two processes are combined to predict overall net migration.

Other uncertainties relate to temporal and geographic scale. As the time period increases so does the uncertainty inherent to the projections, meaning that, for example, the estimates for 2050 are more uncertain than those for 2020. There is also greater uncertainty at the scale of individual countries, compared to the aggregated regional and global projections.

References

UN, 2014, World Population Prospects: The 2012 Revision — Methodology of the United Nations population estimates and projections, Working Paper No. ESA/P/WP.235, United Nations Department of Economic and Social Affairs (UN DESA), New York, US.

Data sets uncertainty

As described in the methodology for gap filling there are challenges relating to the quality of individual countries’ data so the main recorded data set uncertainty is at the level of individual countries.

Rationale uncertainty

N/A