I’ve mentioned unintended consequences. This is not as complicated as it may sound, so I’ll illustrate with a few examples.
In the first case, the result is obvious once you think it through, but it depends on framing the problem properly.
Suppose the roads in your town are very busy. So the town looks at the current traffic volume, projects some future growth, and adds a lane to the major roads to increase capacity.
Because it’s faster to get around, people decide to take more trips. So the traffic volume immediately exceeds the growth projection, and the roads get just as busy as before.
Often we make decisions based on “all other things being equal”. But all other things are rarely equal. Because this system has intelligent agents (people) who make decisions based on the changing characteristics of the system (road capacity as reflected by travel time), any assumptions about a constant traffic load are simply incorrect. Systems can react in this way without intelligent agents, through simple physical, chemical, or operational processes.
What isn’t obvious is that it’s travel time, not road capacity, that drives the behaviour. People don’t care how big the roads are. They only care whether it’s worth the time it takes to get somewhere compared to other options such as public transit.
In general this is called a feedback loop, where a change in one factor leads to a change in another factor in a way that either magnifies or diminishes the first change. More about this later.
The second case is more personal. I had the privilege of fulfilling a lifelong dream to trek in Nepal. The weather was fine and the mountains stupendous. But I felt like I had to pee. Really bad. Nearly all the time. It was uncomfortable, embarrassing, and inconvenient in an area with few toilets. I’m not super shy but getting just a bit of privacy is preferable when going outdoors. Are you getting the picture?
This had happened to me before. I had gone on an awesome bus tour of Buddhist sites in Sri Lanka, and had essentially the same problem. It did happen on occasion at home, but not as bad as on trips. So I assumed perhaps I was getting older and it was my plumbing; or I was not getting enough of the right kinds of fluids; or maybe I had some kind of infection. I had discussed it at some point with a doctor and probably had run a course of antibiotics and tried a couple of other things, but because it wasn’t ahem, pressing, when I was at home, it didn’t get a lot of attention.
So on both trips I just did the best I could, suffered my plight and embarrassment, and still mostly enjoyed myself.
Where does the unintended consequence come in? It was many years later that an internet search revealed that vitamin supplements such as vitamin C, or drinking juice that is acidic such as orange juice, can cause an urge to urinate. Guess what I was doing to stay healthy under demanding conditions or in hot weather? Lots of fluids including juice, and vitamin C supplements.
Since that revelation I am able to observe a direct and immediate correlation between the two. Needless to say, vitamin C supplements are saved for when I’m at home, and my juice consumption is down (also reduces my sugar intake, but that’s a different story).
Generalizing, it’s often the case that many of our problems may be aggravated by their own cures, or by the attempted cures of other problems: a plug for the structured approach to improvement presented earlier.
References
Business Dynamics: Systems Thinking and Modeling for a Complex World by John D. Sterman