13.1 Demographic measures of population aging

Population aging is reshaping societies worldwide. As fertility rates decline and life expectancy increases, the proportion of older individuals grows, impacting social structures and economic systems.

Demographic measures like median age, old-age dependency ratio, and aging index help quantify this trend. Understanding these indicators is crucial for policymakers and researchers to address the challenges and opportunities of an aging population.

Population aging and its indicators

Definition and key measures

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• Population aging the increasing proportion of older individuals in a population over time
  • Typically measured as the percentage of the population above a certain age threshold (65 years and older)
• Key demographic indicators of population aging
  • Median age: the age that divides a population into two numerically equal groups, with half the people being younger than this age and half older
  • Old-age dependency ratio: the number of older dependents (typically those aged 65 and older) relative to the working-age population (usually those aged 15-64)
  • Aging index: calculated as the number of people aged 65 and older per 100 youths under age 15

Drivers of population aging

• Population aging is driven by two main demographic forces
  • Declining fertility rates: lead to a smaller proportion of younger individuals in the population
  • Increasing life expectancy: result in a larger proportion of older individuals in the population
• The combination of these factors leads to a higher proportion of older individuals relative to younger individuals in a population over time

Old-age dependency ratio

Calculation and interpretation

• The old-age dependency ratio is calculated by dividing the number of people aged 65 and older by the number of people aged 15-64 and then multiplying by 100
  • Formula: $\frac{\text{Population aged 65+}}{\text{Population aged 15-64}} \times 100$
• A higher old-age dependency ratio indicates a greater level of population aging and a higher "burden" on the working-age population to support the older population
• Interpreting the old-age dependency ratio requires consideration of:
  • The specific age thresholds used (65+ and 15-64)
  • The cultural, economic, and policy contexts of the population in question

Implications of high old-age dependency ratios

• High old-age dependency ratios can strain social support systems
  • Increased demand for healthcare services and long-term care
  • Greater pressure on pension and retirement systems
• May lead to lower labor force participation rates as a larger proportion of the population reaches retirement age
• Could necessitate changes in policies and programs to address the needs of an aging population (social security, healthcare, housing)

Population pyramids and aging

Interpreting population pyramids

• A population pyramid is a graphical representation of the age and sex structure of a population
  • Horizontal bars represent the proportion of males and females in each age group
• The shape of a population pyramid reflects the extent of population aging
  • More rectangular shape: indicates an older population
  • More triangular shape: indicates a younger population
• An aging population pyramid is characterized by:
  • Narrower base: fewer young people
  • Wider top: more older people

Using population pyramids for analysis

• Comparing population pyramids across time or between different populations can reveal trends in population aging
  • Highlight the demographic forces driving these changes (fertility rates, life expectancy)
• Analyzing population pyramids can provide insights into the potential future demographic trajectory of a population based on the current age structure
  • For example, a population with a large proportion of individuals in their reproductive years may experience population growth in the near future

Chronological vs functional age

Defining the concepts

• Chronological age: the number of years a person has lived since birth
  • Fixed characteristic based solely on the passage of time
• Functional age: an individual's biological, psychological, and social functioning relative to others of the same chronological age
  • More dynamic concept that can vary among individuals of the same chronological age
  • Takes into account factors such as physical health, cognitive abilities, and social engagement

Importance of distinguishing between the two

• The distinction between chronological and functional age is important for understanding the heterogeneity of the older population
  • Recognizes that individuals may "age" at different rates
  • Highlights the limitations of using chronological age alone as a marker of aging
• Policies and programs aimed at supporting older populations should consider both chronological and functional age
  • Better meet the diverse needs of older individuals (healthcare, housing, social services)
  • Avoid a one-size-fits-all approach based solely on chronological age