# 7. The gain around driving Positive Feedback loops A negative feedback loop is self-correcting; a positive feedback loop is **self-reinforcing**. The more it works, the more it gains power to work some more. The more people catch the flu, the more they infect other people. The more babies are born, the more people grow up to have babies. The more money you have in the bank, the more interest you earn, the more money you have in the bank. The more the soil erodes, the less vegetation it can support, the fewer roots and leaves to soften rain and run-off, the more soil erodes. The more high-energy neutrons in the critical mass, the more they knock into nuclei and generate more.
Positive feedback loops are **sources of growth, explosion, erosion, and collapse in systems**. A system with an **unchecked** positive loop ultimately **will destroy itself**. That's why there are so few of them. Usually a negative loop will kick in sooner or later. The epidemic will run out of infectable people--or people will take increasingly strong steps to avoid being infected. The death rate will rise to equal the birth rate--or people will see the consequences of unchecked population growth and have fewer babies. The soil will erode away to bedrock--or people will stop overgrazing, put up check dams, plant trees, and stop the erosion.
Population and economic growth rates are leverage points, because slowing them **gives the many negative loops**- technology and markets and other forms of adaptation, all of which have limits and delays--**time to function**. It's the same as slowing the car when you're driving too fast, rather than calling for more responsive brakes or technical advances in steering.
Another example: Many positive feedback loops in society reward the winners of a competition with the resources to win even bigger next time. Systems folks call them **"success to the successful"** loops. Rich people collect interest; poor people pay it. Rich people pay accountants and lean on politicians to reduce their taxes; poor people can't. Rich people give their kids inheritances and good educations; poor kids lose out. Anti-poverty programs are weak negative loops that try to counter these strong positive ones. It would be **much more effective to weaken the positive loops**. That's what progressive income tax, inheritance tax, and universal high-quality public education programs are meant to do. (If rich people can buy government and weaken, rather than strengthen those of measures, the government, instead of balancing "success to the successful" loops, becomes just another instrument to reinforce them!)
The most interesting behavior that rapidly turning positive loops can **trigger** is **chaos**. This wild, unpredictable, unreplicable, and yet bounded behavior happens when a **system starts changing much, much faster than its negative loops can react to it**. For example, if you keep raising the capital growth rate in the world model, eventually you get to a point where one tiny increase more will shift the economy **from exponential growth to os-cillation**. Another nudge upward gives the oscillation a double beat. And just the tiniest **further nudge sends it into chaos**.
I don't expect the world economy to turn chaotic any time soon (not for that reason, anyway). That behavior occurs only in unrealistic parameter ranges, equivalent to doubling the size of the economy within a year. **Real-world systems can turn chaotic, however, if something in them can grow or decline very fast.** Fast-replicating bacteria or insect populations, very infectious epidemics, wild speculative bubbles in money systems, neutron fluxes in the guts of nuclear power plants; these systems can turn chaotic. **Control must involve slowing down the positive feedbacks.**
In more ordinary systems, look for leverage points around birth rates, interest rates, erosion rates, "success to the successful" loops, any place where the more you have of something, the more you have the possibility of having more.