Life Expectancy

Life expectancy definition

This is based on several factors such as year of birth, current age, sex, and demographic location.

Your life expectancy is very dependent on demographic conditions, which is why you often see people in less developed countries have a lower life expectancy than those living in more developed countries.

Things that can (drastically) reduce your life expectancy include the prevalence of infectious diseases, poor health care, and lack of access to a clean water supply.

Life expectancy (figure 1) is not to be confused with lifespan. The latter is the maximum amount of years that any species can live. At the moment, the lifespan of humans is over 120 years.

Life expectancy at birth (LEB)

LEB is defined as an average of how long a newborn can expect to live, providing that the current death rates do not change. LEB is one of the most used health indicators.

While the LEB indicates the average number of years a newborn can expect to live, it is not set in stone. It is just an indicator and, as mentioned earlier, heavily dependent on specific factors. When a person has access to better health care, they can live past the life expectancy given at birth.

While this sounds simple enough, it is different in practice. One crucial distinction is the difference between cohort life expectancy and period life expectancy.

The image below (figure 1) shows the global life expectancy at birth.

Figure 1: Global life expectancy at birth 2019, Fnweirkmnwperojvnu/Wikimedia Commons, CC BY-SA 4.0

Cohort life expectancy

Before explaining what this means, you must know what the term cohort means in this context.

The cohort life expectancy is the average life length of a particular cohort. This life expectancy is calculated by observing a combination of mortality rates for the past years and future projections for the specific cohort in the coming years. Just remember that these are projections, not forecasts. Future changes could mean that the cohort life expectancy will change for better or worse.

Period life expectancy

Period life expectancy looks at things from a different perspective. It looks at mortality rates from a single year or a group of years and assumes that those rates apply throughout the remainder of a person's life. That means that any future changes in mortality rate are not taken into account.

Considering that this life expectancy does not consider future projections, it can give a more objective view. It is, therefore, used more often than the cohort life expectancy. That being said, period life expectancies tend to be lower for the same reason, because they do not consider any future projections and assumptions.

Health-adjusted life expectancy (HALE)

HALE is the average number of years a person is expected to live in good health. That means that this person has not suffered from disabling illness or injuries. This measurement is used by the World Health Organization (WHO) to assess the health and well-being of a country.

HALE considers the years a person lived in less-than-full health due to a disease or injury.

The table below shows the HALE at birth by global region for 2019.

Environmental risks

The environment directly affects health status and plays a significant role in the quality of life, years of healthy life lived, and health disparities. Therefore, this ties in with HALE.

Poor air quality, caused by pollution, is one example linked to premature death, cancer, and long-term damage to someone's respiratory and cardiovascular systems.

The World Health Organization (WHO) conducted a study showing that nearly 1 in 4 deaths are linked to unhealthy environments¹.

The WHO states that cancers are the leading cause of death worldwide, with around 19% of those cancers being attributed to environmental factors.

Environmental quality survey template

Surveys are conducted to assess how people feel about environmental and local issues. There are 3 reasons such surveys are used:

1. To evaluate people's perception of environmental degradation
2. Data is collected to evaluate the common factors causing environmental degradation
3. Evaluate the purchase behaviour of people, for example, do they purchase the more expensive, environmental-friendly products

There are many different templates for such surveys, below is an example of an environmental quality survey.

Life expectancy countries

Every country has a different life expectancy; the map below (figure 2) shows the life expectancy at birth in the different countries, based on the statistics known for 2019.

Figure 2: Map of life expectancy around the world in 2019 - Our World In Data (2005)

It is worth remembering that the map shows average life expectancy for both sexes, not separately.

Average life expectancy - meaning

The average life expectancy means that it looks at an average of the numbers. This can be an average between men and women, an average of all the countries in the world or a region, or a combination.

The life expectancy of men in 2020

As mentioned earlier, men have a lower life expectancy than women on average. The table below (table 1) shows you the different global average life expectancies, based on the statistics from 2020.

Table 1

The following table (table 2) shows the average life expectancy for the UK in 2020.

Table 2

Life expectancy rising

The average life expectancy is rising on a global scale, with people now living, on average, twice as long as opposed to the early 19th century. One of the most important increases in this life expectancy is the decline in child mortality.

The maps below (figure 3) show the world's life expectancy in 1800, 1950, and 2015, showing a clear rise in life expectancy.

Figure 3: Map showing life expectancy in 1800, 1950, and 2015 - Our World In Data (2005)

What is apparent when looking at the maps is that, in general, the increase is less and less steep in less-developed countries, such as several countries in Africa. This shows there is still a lot of inequality.

Reasons for the poor life expectancy in the 1800s include high child mortality. Children and young adults died mainly due to poor health measures, such as effective medicines to fight infectious diseases. Poor health measures, infectious diseases, local conflicts, and poor infrastructure such as water supplies are still the main reasons for the lower life expectancy in certain countries.

The maps below (figures 4 and 5) show the population expected to survive to the age of 69 (as of 2019).

Figure 4: Map showing the share of men expected to survive to the age of 65 - Our World In Data (2021)

Figure 5: Map showing the share of women expected to survive to the age of 65 - Our World in Data (2021)

These maps show you that more women are expected to survive to the age of 65, compared to men. As data has shown throughout the decades, women generally tend to live longer than men.

Calculating life expectancy

Life tables that present age-specific mortality rates are used to calculate life expectancy. The life expectancy tables are calculated based on death probabilities according to Farr's death rate method:

qx = Mx / (Bx + (Mx/2))

• Mx = number of deaths at the age of x to under x+1 years in the reported period.
• Bx = average population aged x to under x+1 in the base period
• qx = death probability from age x to x+1

As mentioned earlier, life expectancy is not a set statistic. It can change for several reasons, for better or for worse. The calculator and the outcomes it generates are averages.

There are also plenty of life expectancy calculators online that you can use; however, they are less accurate as they do not consider some important aspects that attribute to a higher or lower life expectancy.

References and figures:

1. WHO: Preventing disease through healthy environments. https://www.who.int/publications/i/item/9789241565196

Figure 2: Data from Riley, J.C. (2005) Life expectancy 2019 via Our World in Data.

Figure 3: Data from Riley J.C. (2005) Life expectancy 2019 via Our World in Data.

Figure 4: Data from World Bank (2021) World Population Prospects - UN Population Division (2019) via Our World in Data.

Figure 5: Data from World Bank (2021) World Population Prospects - UN Population Division (2019) via Our World in Data.