The great acceleration

Activity title

Growth Simulation

Overview

Participants simulate linear growth and exponential growth. 

Objectives

• To get a sense of the dynamic of exponential growth

Materials

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Time

According to the group size, between 5 and 15 minutes

Group size

Works for all group sizes

Instructions for trainers

1. For this exercise participants must sit in a classroom setting (in rows). In the case that participants are sitting in a circle, ask them to put their chairs into a classroom setting (rows next to AND in front of each other). 
2. Explain to participants that you will now simulate linear growth. Therefore, the first student should stand up and tap the participant next to them on the shoulder. After being tapped on the shoulder, this and every further participant stands up and taps the next person, until the whole group is standing. Meanwhile you time the group. 
3. Tell the group how long the linear growth simulation took. 
4. Explain to participants that the group will, in a few moments, simulate exponential growth. Explain that the participant in the middle of the middle row (i.e. the most central participant) should start by standing up and tapping two other participants on their shoulders. Those two and all other participants continue the process by standing up and tapping two further participants until they are all standing.
5. Ask the participants to guess how long it will take the group until all participants are standing. 
6. Carry out the activity to simulate exponential growth (the simulation is only an approximation of exponential growth, it is a bit slower than exponential growth).
7. Conclusion: Whenever we talk about how much an economy grows (in percentage points) we talk about exponential growth. This is because the basis from which the growth is calculated does not stay the same (as with linear growth), but itself grows every year. This growing basis leads to a completely different dynamic than linear growth. 

Debriefing and evaluation

Exponential growth describes a process in which the size of stock always changes by the same factor in equal time steps. Therefore, the rate of increase itself increases dramatically with time. A well-known example of exponential growth in biophysical processes is the spread of water lilies. If there are 10 water lilies on the surface of a pond in one week and 20 in the next, many intuitively assume that one week later there will be 30, then 40 and then 50. This is the linear view of the world which is familiar to us. In fact, there will be 40, then 80, then 160, and in the week before the pond is completely covered with water lilies, they will have only covered half of the pond. Whenever we speak about economies that grow e.g. 3% yearly, we are speaking about exponential growth. Therefore, a yearly growth of 3% leads to an economy being double the initial size in only 24 years. 

Tips for trainers

This video shows how it works: https://www.youtube.com/watch?v=1_SwKG4Zt60

Challenges that might occur:  If participants sit very far from each other and cannot really reach each other the simulation might not work that well, or it is at least slower. 

Remark:  If participants have tables with water bottles, laptops, etc. in front of them, warn them to take care of their items when standing up, so that nothing breaks.