Mortality rate in the context of "World population"

Sub-replacement fertility is a total fertility rate (TFR) that (if sustained) leads to each new generation being less populous than the older, previous one in a given area. The United Nations Population Division defines sub-replacement fertility as any rate below approximately 2.1 children born per woman of childbearing age, but the threshold can be as high as 3.4 in some developing countries because of higher mortality rates. Taken globally, the total fertility rate at replacement was 2.33 children per woman in 2003. This can be "translated" as 2 children per woman to replace the parents, plus a "third of a child" to make up for the higher probability of males born and mortality prior to the end of a person's fertile life. In 2023, the global average fertility rate was around 2.2 children born per woman.

Replacement-level fertility in terms of the net reproduction rate (NRR) is exactly one, because the NRR takes both mortality rates and sex ratios at birth into account.

Human life expectancy is a statistical measure of the estimate of the average remaining years of life at a given age. The most commonly used measure is life expectancy at birth (LEB, or in demographic notation e₀, where e_x denotes the average life remaining at age x). This can be defined in two ways. Cohort LEB is the mean length of life of a birth cohort (in this case, all individuals born in a given year) and can be computed only for cohorts born so long ago that all their members have died. Period LEB is the mean length of life of a hypothetical cohort assumed to be exposed, from birth through death, to the mortality rates observed at a given year. National LEB figures reported by national agencies and international organizations for human populations are estimates of period LEB.

Human remains from the early Bronze Age indicate an LEB of 24. In 2019, world LEB was 73.3. A combination of high infant mortality and deaths in young adulthood from accidents, epidemics, plagues, wars, and childbirth, before modern medicine was widely available, significantly lowers LEB. For example, a society with a LEB of 40 would have relatively few people dying at exactly 40: most will die before 30 or after 55. In populations with high infant mortality rates, LEB is highly sensitive to the rate of death in the first few years of life. Because of this sensitivity, LEB can be grossly misinterpreted, leading to the belief that a population with a low LEB would have a small proportion of older people. A different measure, such as life expectancy at age 5 (e₅), can be used to exclude the effect of infant mortality to provide a simple measure of overall mortality rates other than in early childhood. For instance, in a society with a life expectancy of 30, it may nevertheless be common to have a 40-year remaining timespan at age 5 (but not a 60-year one).

Birth rate, also known as natality and the crude birth rate, is the total number of live human births per 1,000 population for a given period divided by the length of the period in years. The number of live births is normally taken from a universal registration system for births; population counts from a census. The birth rate (along with mortality and migration rates) is used to calculate population growth. The estimated average population may be taken as the mid-year population.

When the crude death rate is subtracted from the crude birth rate (CBR), the result is the rate of natural increase (RNI). This is equal to the rate of population change (excluding migration).

The ageing of Europe, also known as the greying of Europe, is a demographic phenomenon in Europe characterised by a decrease in fertility, a decrease in mortality rate, and a higher life expectancy among European populations. Low birth rates and higher life expectancy contribute to the transformation of Europe's population pyramid shape. The most significant change is the transition towards a much older population structure, resulting in a decrease in the proportion of the working age while the number of the retired population increases. The total number of the older population is projected to increase greatly within the coming decades, with rising proportions of the post-war baby-boom generations reaching retirement. This will cause a high burden on the working age population as they provide for the increasing number of the older population.

Throughout history many states have worked to keep high birth rates in order to have moderate taxes, more economic activity and more troops for their military.

Demographic transition is a phenomenon and theory in the social sciences (especially demography) referring to the historical shift from high to low rates of birth and death, as societies attain several attributes: more technology, education (especially for women), and economic development. The demographic transition has occurred in most of the world over the past two centuries, bringing the unprecedented population growth of the post-Malthusian period, and then reducing birth rates and population growth significantly in all regions of the world. The demographic transition strengthens the economic growth process through three changes: reduced dilution of capital and land stock; increased investment in human capital; and increased size of the labor force relative to the total population, along with a changed distribution of population age. Although this shift has occurred in many industrialized countries, the theory and model are often imprecise when applied to individual countries, because of specific social, political, and economic factors that affect particular populations.

Nevertheless, the existence of some type of demographic transition is widely accepted because of the well-established historical correlation between two factors: dropping fertility rates, and social and economic development. Scholars debate whether industrialization and higher incomes lead to lower population, or vice versa. Scholars also debate to what extent various proposed and sometimes interrelated factors are involved—factors such as higher per capita income, lower mortality, old-age security, and increased demand for human capital. Human capital gradually increased during the second stage of the Industrial Revolution, which coincided with the demographic transition. The increasing role of human capital in the production process led families to invest this capital in children, which may have been the beginning of the demographic transition.

The population of the United Kingdom was estimated at 69.3 million in 2024. It is the 21st most populated country in the world and has a population density of 285 people per square kilometre (740 people/sq mi), with England having significantly greater density than Wales, Scotland, and Northern Ireland. Almost a third of the population lives in south east England, which is predominantly urban and suburban, with 9,089,736 people in the capital city, London, whose population density was 5,782 inhabitants per square kilometre (14,980/sq mi) in 2024.

The population of the UK has undergone demographic transition— from a typically pre-industrial population, with high birth and mortality rates and slow population growth, through a stage of falling mortality and faster rates of population growth, to a stage of low birth and mortality rates with, again, lower rates of growth. This growth through 'natural change' has been accompanied in the past three decades by growth through net immigration into the United Kingdom, which since 1999 has exceeded natural change.

Human population projections are attempts to extrapolate how human populations will change in the future. These projections are an important input to forecasts of the population's impact on this planet and humanity's future well-being. Models of population growth take trends in human development and apply projections into the future. These models use trend-based-assumptions about how populations will respond to economic, social and technological forces to understand how they will affect fertility and mortality, and thus population growth.

The 2022 projections from the United Nations Population Division (chart #1) show that annual world population growth peaked at 2.3% per year in 1963, has since dropped to 0.9% in 2023, equivalent to about 74 million people each year, and could drop even further to minus 0.1% by 2100. Based on this, the UN projected that the world population, 8 billion as of 2023, would peak around the year 2084 at about 10.3 billion, and then start a slow decline, assuming a continuing decrease in the global average fertility rate from 2.5 births per woman during the 2015–2020 period to 1.8 by the year 2100 (the medium-variant projection).