9.1 Components of population change

Population change is driven by three key factors: fertility, mortality, and migration. These components interact to shape the size and structure of populations over time, influencing growth or decline in complex ways.

Understanding these components is crucial for grasping demographic transitions. As societies develop, the relative importance of each factor shifts, leading to changes in population dynamics and age structures. This interplay forms the basis for population projections and policy decisions.

Population Change Components

Key Factors Influencing Population Dynamics

Top images from around the web for Key Factors Influencing Population Dynamics

• 

  World Population Growth - Our World in Data View original

  Is this image relevant?

• 

  Demographic Theories | Introduction to Sociology View original

  Is this image relevant?

• 

  ESS Topic 8.1: Human Populations Dynamics - AMAZING WORLD OF SCIENCE WITH MR. GREEN View original

  Is this image relevant?

• 

  World Population Growth - Our World in Data View original

  Is this image relevant?

• 

  Demographic Theories | Introduction to Sociology View original

  Is this image relevant?

1 of 3

Top images from around the web for Key Factors Influencing Population Dynamics

• 

  World Population Growth - Our World in Data View original

  Is this image relevant?

• 

  Demographic Theories | Introduction to Sociology View original

  Is this image relevant?

• 

  ESS Topic 8.1: Human Populations Dynamics - AMAZING WORLD OF SCIENCE WITH MR. GREEN View original

  Is this image relevant?

• 

  World Population Growth - Our World in Data View original

  Is this image relevant?

• 

  Demographic Theories | Introduction to Sociology View original

  Is this image relevant?

1 of 3

• Fertility (births) number of live births occurring in a population during a specific time period
  • Typically measured by the crude birth rate or total fertility rate
  • Crude birth rate number of live births per 1,000 population in a given year
  • Total fertility rate average number of children a woman would have if she experienced the current age-specific fertility rates throughout her reproductive life
• Mortality (deaths) number of deaths occurring in a population during a specific time period
  • Typically measured by the crude death rate or life expectancy
  • Crude death rate number of deaths per 1,000 population in a given year
  • Life expectancy average number of years a person can expect to live at a given age, based on current mortality rates
• Migration movement of people into (immigration) or out of (emigration) a population
  • Can occur within a country (internal migration) or between countries (international migration)
  • Internal migration examples rural-to-urban migration, displacement due to natural disasters or conflicts
  • International migration examples labor migration, refugee movements, student mobility

Demographic Balancing Equation

• Population change over time determined by the balance between births, deaths, and migration
• Demographic balancing equation: $Population_{t+1} = Population_t + Births - Deaths + Immigrants - Emigrants$
  • $Population_{t+1}$ population size at the end of the time period
  • $Population_t$ population size at the beginning of the time period
  • $Births$ number of live births during the time period
  • $Deaths$ number of deaths during the time period
  • $Immigrants$ number of people moving into the population during the time period
  • $Emigrants$ number of people moving out of the population during the time period

Births, Deaths, and Migration

Impact on Population Growth or Decline

• Population growth occurs when births + in-migrants > deaths + out-migrants
  • Example high fertility rates and immigration in many developing countries
• Population decline occurs when deaths + out-migrants > births + in-migrants
  • Example low fertility rates and aging populations in many developed countries
• Rate of natural increase (or decrease) crude birth rate - crude death rate, expressed as a percentage
  • Example if crude birth rate is 20 per 1,000 and crude death rate is 8 per 1,000, rate of natural increase is 1.2%
• Net migration rate (in-migrants - out-migrants) / population size, expressed as a percentage
  • Example if a country has 50,000 immigrants and 30,000 emigrants, with a population of 1 million, net migration rate is 2%
• Overall population growth rate rate of natural increase + net migration rate
  • Example with a rate of natural increase of 1.2% and a net migration rate of 2%, overall population growth rate is 3.2%

Age Structure and Population Momentum

• Births, deaths, and migration can significantly impact a population's age structure
• Age structure relative proportion of individuals in different age groups within a population
  • Typically represented using a population pyramid
  • Example expansive pyramid with a wide base (many young people) and narrow top (few elderly)
• Population momentum continued population growth even after fertility rates decline, due to a large proportion of women in reproductive ages
  • Occurs when a population has a young age structure and fertility rates have recently declined
  • Example many countries in sub-Saharan Africa experiencing population momentum despite declining fertility rates

Component Importance in Dynamics

Relative Importance Across Populations and Time

• Fertility, mortality, and migration shape population dynamics differently across populations and over time
• Developing countries high fertility rates often the primary driver of population growth
  • Mortality rates have declined due to improvements in health and living conditions (sanitation, vaccination, access to healthcare)
  • Example many countries in Africa and South Asia with high fertility rates and declining mortality rates
• Developed countries low fertility rates and aging populations lead to greater reliance on immigration for population growth or stability
  • Example many countries in Europe and East Asia with below-replacement fertility rates and significant immigrant populations
• Out-migration can lead to population decline, even with relatively high fertility rates
  • Often due to economic, political, or environmental factors (job opportunities, conflict, climate change)
  • Example countries in Eastern Europe experiencing population decline due to high levels of emigration

Demographic Transition Model

• Illustrates how the relative importance of fertility and mortality in shaping population dynamics changes as societies develop and modernize
• Stage 1 (pre-industrial) high fertility and high mortality, slow population growth
• Stage 2 (early transition) high fertility and declining mortality, rapid population growth
• Stage 3 (late transition) declining fertility and low mortality, slowing population growth
• Stage 4 (post-industrial) low fertility and low mortality, stable or declining population
• Stage 5 (second demographic transition) very low fertility and low mortality, population decline or reliance on immigration
  • Example many countries in Europe and East Asia currently in Stage 4 or 5 of the demographic transition

Interplay of Population Change Components

Interconnectedness and Complexity

• Fertility, mortality, and migration are interconnected and influence each other in complex ways
• Changes in fertility rates impact age structure, which affects mortality rates and migration patterns
  • Example high fertility rates lead to a young population, which can result in lower mortality rates and increased migration for employment or education
• Migration alters the age, sex, and ethnic composition of a population, with implications for fertility and mortality rates
  • Example immigration of young adults can boost fertility rates and lower the median age of a population
  • Emigration of working-age adults can accelerate population aging and increase the dependency ratio
• Economic, social, and political factors simultaneously influence fertility, mortality, and migration
  • Can lead to synergistic or counteracting effects on population dynamics
  • Example economic recession can lead to lower fertility rates, increased out-migration, and potentially higher mortality rates due to reduced access to healthcare

Unintended Consequences of Population Policies

• Population policies aimed at influencing one component of population change can have unintended consequences on other components
• Promoting family planning to reduce fertility can lead to increased out-migration due to reduced job opportunities
  • Example as fertility rates decline, there may be less demand for teachers, healthcare workers, and other professionals serving children and families
• Encouraging immigration to address labor shortages or population aging can impact fertility rates and ethnic composition
  • Example immigrants from high-fertility countries may contribute to increased fertility rates in the host country
  • Increased cultural diversity due to immigration can lead to social tensions or changes in political attitudes towards migration
• Policies addressing mortality (healthcare access, public health interventions) can affect fertility and migration decisions
  • Example improved child survival rates may lead to lower desired family sizes and reduced fertility rates
  • Increased life expectancy may result in more people migrating to access better healthcare services or to retire in areas with favorable living conditions