The aging of the world population comes from two facts: people are living longer and are having fewer babies. 

Social scientists use a model of demographic transition to explain that the process of moving from a young, growing population to an older, stable population is tied to the economic and technological development of a society.

In this model, a country starts with a really high birthrates and really high death rates, resulting in a population with a lot of very young people, but not much overall population growth.

Then agricultural and technological advancements improve the standards of living. Access to food, water, housing, and medical treatment all improve, which reduces the number of people who are dying at a young age.

People are still having a lot of children, but they're living longer, so this leads to a large and older population. But then, in the next phase in the model, as the probability improves that a child will live into adulthood, families begin having fewer children.

So their country reaches the final stage of demographic transition: low birthrates and stable death rates. And if there are fewer babies, that means there are fewer young people to pull down the average age.

The total fertility rate, which is a projected estimate olf teh number of children an average woman of childbearing age will have over her lifetime has been declining for most countries for a while now. 

For the United States, total fertility rates were at a peak of 3.7 births per woman in the late 1950s, but are now only at 1.8 births per woman. All of this means that we're looking at a future with a few more grey heads in society than past generations have had.

So what does that mean for society? Before we can answer that question, let's look at some of the ways that sociologists understand aging. Aging is a biological, psychological, and cultural experience.

The biological part you probably already know apart. Aging increases risk factors for many diseases, particularly chronic diseases such as arthritis, heart disease, and diabetes. 78% of Americans age 55 and older have at least one chronic condition.

As infectious diseases like smallpox or tuberculosis become a thing of the past in high-income countries, chronic diseases have become the leading cause of death in those countries. That said, it's not like everyone over th age of 55 is teetering on the brink of the grave.

As life expectancy increases, the age at which people first begin experiencing chronic illnesses is often also postponed. This compression of morbidity, a term coined by a doctor and professor of medicine, James Fries, means that most people in high-income countries live healthy lives for the majority of their lives, and then experience rapid health declines compressed into the end of life.

Which I guess is good? But there's a lot of variation in illness and mortality rates across demographic groups. Wealthier elderly people are less likely to face health challenges than the poorer elderly. Women tend to live longer than men, but that also means that they're more likely to suffer from chronic disabilities like arthritis.

Why we age and how we age are still major questions within biology, genetics, and medicine. Senescence is the process of becoming old - which includes all the physical or mental deterioration that comes along with age.

There are two main schools of thought in modern biological theories as to why senescence happens: error versus programming. 

Error theories, also known as wear and tear theories, focus on ways on which damage to cells and tissue accumulate over time and explore how aging is a result of damage to or deterioration of key cells in the body.

Programming theories, also known as aging clock theories, focus on how the body switches on or off certain biological processes as you reach a certain age. For example, the immune system is at its peak during puberty and slowly declines as you age, meaning that it's harder for your body to fight off any diseases when you're older.

Along with the biological changes that people experience when they age, there are also psychological changes. Older adults are at a higher risk for dementia, including Alzheimer's Disease and other types of cognitive impairment than younger adults.

Thankfully, old age doesn't mean drastic psychological decline for most people. Only about 7% of adults over the age of 70 suffer from memory loss or more serious mental deterioration.

While the biological and psychological parts of aging are pretty well known, it's the cultural part of aging that I want to highlight today. How is aging perceived by society? Does being older mean that other people see you as a wise elder or as a washed-up dinosaur?

Like race or gender, age is a trait that influences a person's social position in the world. Age stratification is the unequal distribution of wealth, power, and privilege among people at different stages of life.

And, of course, different cultures value their older citizens differently. Historically, if we were to compare hunter-gatherer societies where survival relied on physical strength with agrarian societies where food can be stored up, the elderly may be more likely to be seen as a burden in the former than the later.

But once it's possible to build up wealth, some people may be able to accumulate money and power over time, leading to greater privilege for an older person than a younger person.

A gerontocracy is a form of social organization in which the older members of society have the most wealth, power, and prestige. As nations industrialize, however, the main source of income shifts from land ownership to income from work, and many older people move out from paid labor, whether it's by choice or because it becomes more difficult to find a job as you age.

Only about 18% of Americans over the age of 65 report being employed either full- or part-time. Nowadays, rapidly changing technology means that many older workers are finding it harder to compete with younger workers.

Some of this is simply due to changes in what types of jobs are available, which may make the job experience of older workers less relevant in today's economy.

But companies may also be less willing to hire older workers because of ageism or prejudice and discrimination based on age. Employers may unfairly generalize about the abilities of older workers, thinking that all older workers will be less productive or less up to date on the skills needed for the job.

This is partially why we see so much stratification among older Americans. They're much more vulnerable to poverty, with 8.8% of Americans over the age of 65 living in poverty.

Retirement from the labor force is, of course, voluntary for many people in high-income countries. And for some, it's a welcome break from the workforce. But for others, i'ts a difficult transition for both financial and cultural reasons.

While many wealthier countries provide some kind of income support for the elderly like social security in the US, retirement is generally only feasible for those who save enough during their working years to live comfortably after they've stopped working.

In economic downturns like the Great Recession, the value of people's retirement savings will often plummet, forcing people to work further into old age than they intended to.

But even for those who are able to retire, retirement can still be a difficult life transition. Especially in the US, many feel that their identity ans self-worth is tied up with their profession.

After all, what's the first question that you ask someone when you meet them at a party? "So, what do you do?"

When work plays such a central role in society, retiring can result in less social prestige as well as a loss of purpose. For some retired people, work and the labor market ends up being replaced with care-giving work. 

Caregiving here refers to informal, unpaid care provided to a dependent by family members, other relatives, or friends. About 42% of caregivers to teh elderly are a spouse, more likely a wife taking care of a husband than the other way around, partially due to women's longer lifespans.

Caregiving is a demanding job and can contribute to the social isolation that many older members of society feel. Limited time due to care-giving, lower mobility due to the aging process or chronic health problems, and the loss of aging friends and family members are all reasons that older Americans cite for feeling lonely or isolated as they age.

Death is a bit of a grim note to end our discussion of aging on, but just as aging plays as specific cultural role, so does death. And as the saying goes, "nothing is certain in life except death and taxes."

Observing how death plays out in a society helps us understand the values and beliefs of a society. What is considered a good death?

Death in modern society tends to be culturally removed from our day-to-day life, partially due to our longer lifespans. Nowadays, rather than dying at home surrounded by families and friends, many people die in healthcare settings like hospitals.

The ethics of how doctors and patients navigate medical choices as someone nears the end of their life is a topic that's fraught with difficulties.

Some patients leave living wills that explicitly state their preferences for treatment, but oftentimes these decisions end up in the hands of family members and doctors who may disagree on the best decision to make.

How to people react to nearing the end of their lives or to the death of people that they love? You might have heard of the Five Stages of Grief: denial, anger, negotiation, resignation, and acceptance.

Though psychologist Elizabeth Kubler Ross originally developed this as a model for how people confront their own death, it has come to be seen as a model for how people deal with the death of those they love as well. 

Understanding how we as people process death and aging will only take on more importance in the coming years as the number of older people in society increases.

Today we learned about the changing age patterns of the world. We discussed the biological, psychological, and cultural aspects of aging. And finally, we ended with a discussion of some of the difficulties faced by older individuals, including economic instability, retirement, care-giving, social isolation, and navigating medical decisions as they near the end of life.

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