Reinforcing Loop

A reinforcing loop is one in which an action produces a result which influences more of the same action thus resulting in growth or decline. The reinforcing loop is one of the two foundational structures of systems thinking, the other being the Balancing Loop. Consider the following example which describes a savings account.

Periodically the principal in the savings account interacts with the interest rate and adds to the interest. The interest rate in this example is assumed to be constant. The interest then adds to the principal causing it to increase. In the next period the cycle repeats, only now the principal is greater than it was before so it's interaction with the interest rate adds an even greater amount to the interest. This larger interest then again adds to the principal. The graph to the right above principal shows the resultant growth of the principal.

Because of the manner in which this structure reinforces itself it generally produces an exponential growth or decline. This exponential change may be unnoticeable for a period of time until it reaches a certain threshold. The structure then seems to change very rapidly causing one to wonder how it began all at once, when in fact it really didn't. The growth just wasn't substantial enough to be noticed.

Effective Strategies

If a reinforcing structure is producing a desirable result it is generally referred to as a virtuous cycle. When this happens there is a tendency to ignore it and let it go. This is a mistake, as nothing grows forever. When everything is going just they way you want it to that's the best time to be concerned about how to ensure it continues going the way you want it to.
When a reinforcing structure is producing an undesirable result it is generally referred to as a viscous cycle. The best way to deal with a viscous cycle is to find a way to break one of the feedback loops so the structure can no longer reinforce itself.

Areas of Concern

The reinforcing structure is one of the simplest structures and seldom ever occurs in isolation from additional influences. As was indicated above, nothing grows forever so there are extensions of this structure to be concerned about. The most prevalent extensions of the reinforcing structure are identified in the following areas of concern.

It has been repeatedly indicated that nothing grows forever. What often happens with a reinforcing structure is that there are limits to growth which have not yet kicked in. The best thing to do is look for these before you run into them. For insights into this situation see Limits to Growth.
Since you can't create something from nothing, the growth comes with a cost somewhere. Consider whether the growth is creating a decline somewhere else you haven't quite noticed as of yet. For insights into this situation see Success to the Successful.
Often the reinforcing nature of this structure is the result of a synergistic relation between two or more individuals, groups, or organizations. When this is the case there is a tendency for the involved parties to take unenlightened action with actually destroys the synergy. For insights into this situation see Accidental Adversaries.

Examples

The following examples are intended to provide some specific instances in which a reinforcing structure is the primary structure.