choose the future!
Exponential growth
Most of the issues humanity faces involve exponential growth in some way. To really understand the seriousness of those issues we must first understand exponential growth.
Many things grow, but not all things grow in the same way. There are two basic ways for something to grow: linearly, and exponentially. When something grows linearly it grows repeatedly by the same amount; when something grows exponentially it grows repeatedly by the same proportion.
These graphs show the different character of linear growth and exponential growth:
Both graphs show that what is being measured increases from left to right. The left-hand graph shows linear growth: what is being measured increases at steady rate, giving a rising straight line. The right-hand graph shows exponential growth: what is being measured increases at an ever increasing rate, giving a continually steepening curve.
The long-term outcome of each type of growth is very different: the outcome of linear growth is intuitive; the outcome of exponential growth isn't, and it's very surprising.
To understand the seriousness of the issues humanity faces we need to understand the consequences of exponential growth. These consequences can be condensed down to these two important simple points about exponential growth:
exponential growth produces huge increases unexpectedly quickly
most of the growth happens at the very end of the process
Whenever we are looking at something that is growing exponentially, it is important to look at that growth with these two points in mind.
Remember: anything that grows repeatedly by the same proportion is growing exponentially, so anything that grows by the same percentage every year is growing exponentially; this includes the economy, inflation, population; and because the economy and population are growing exponentially: energy consumption, resource use, food demand, water demand, and land use. Most of these real-life things don't grow at a perfectly exponential rate, but nevertheless the essential character of their growth is exponential.
Understanding the nature of exponential growth is essential to understanding these issues.
More information and ideas
This section of choose the future! gives only a very brief overview of the nature of exponential growth. For a deeper, but still easy to understand examination of exponential growth there is other excellent information on the web.
This section of choose the future! is loosely based on the content of Dr. Albert Bartlett's lecture Arithmetic, Population and Energy. Dr. Albert Bartlett is Professor Emeritus in Nuclear Physics at University of Colorado at Boulder, USA.
Dr. Albert Bartlett's presentation is surprisingly fun and entertaining as well as being informative and easy to understand. The lecture can be viewed at his website. A transcript of the lecture is also available.
Chapter 4 of Chris Martensen's Crash Course, Compounding is the Problem, gives an interesting and illuminating description and example of exponential growth.
World Population Balance provides a short slide show that gives another view on exponential growth, particularly its relationship to population growth.
For a much broader and deeper examination of exponential growth see The Exponentialist website.
This page is linked from:
resource recycling and economic growth
decoupling the economy from resource use
underpinnings – supporting concepts
blog post: will renewables save us?
the consequences of easy energy
blog post: problems with trams
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