Age and Ageing

A white man is crouched down next to several seedlings. A dozen or so Indian men (to his left) and women (to his right) form a circle around him.
A development worker teaches people in Tiruvannamalai, India, about contour planting. Such development projects promise to improve the livelihoods of people in poor countries, but there are many questions about what policies and programs are effective.
photo from Flickr/treesftf

Demographics of Youth and Age [Link]

When studying age-related phenomena, it is important to distinguish between age effects and cohort effects. If a difference between people of different ages is due to an age effect, then each individual's characteristics will change as they go through their life cycle. For example, in the US, wealth is lowest among young adults, higher in middle age, and then lower again among the elderly. An individual person will on average start out with less money, then become richer as their career advances, then become poorer again as they transition to a fixed retirement income. A cohort effect is when age-related differences are the result of relatively stable differences between groups of people born at different times. A cohort is a group of people born within a particular time frame (often 5-10 years, e.g. the cohort of people born between 1990 and 1995). For example, in the US support for same-sex marriage is lower among older people than among younger people. This is not because people change their views on marriage as they age -- rather, each cohort forms their views about marriage early in life and then carries them along through their life, and it happens that each cohort has been forming more favorable views on same-sex marriage than the ones before them. So in ten years, the people who are currently 50-59 years old will be 60-69, and they will have more favorable views of same-sex marriage than today's 60-69-year-olds.

Life Cycles and Movement [Link]

Building Landscapes for Seniors and Youth [Link]

Age and Nature [Link]

Map of world GDP per capita
Figure 1: World GDP per capita.
data from ...

Works Cited

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