Simple Rules

A Way to Navigate Complexity

what are simple rules

Think of situations that you deal with repeatedly in your life; complex ones like deciding how to spend money, hiring/firing decisions or simple ones like what pair of shoes to buy. What is your default way of making these calls? Most people will go through an evaluation process in an effort to make the right decision, typically without explicitly considering time to decision or consistency in making similar decisions.

Simple rules are an alternative approach that aims to make fast and consistent decisions. We have all encountered these rules in the form of advice on a specific topic, something like when buying shoes always get a black pair that are comfortable and don’t look flashy (these are my rules, although I dabbled with green shoes for a while).

The idea is, sometimes (most of the time in my opinion, will cover why later in this post) fast, good enough decisions are what is needed.

Let’s look at real life examples of simple rules to hammer in the idea further. The first story from Gerd Gigerenzer’s book Risk Savvy: How to Make Good Decisions

On a sunny January afternoon in 2009, 150 passengers boarded US Airways Flight 1549. Three minutes after they took off from LaGuardia airport in New York City, something happened out of the blue. A flock of Canada geese approached the plane, in perfect formation. At an altitude of twenty-eight hundred feet, passengers and cabin crew suddenly heard loud bangs. The geese had collided with the engines. A jet engine can “ingest” smaller birds but not Canada geese weighing ten pounds or more. If the bird is too big, the engine shuts down rather than exploding. But this time the improbable event had happened: The geese had flown into not just one but both engines, and both were silenced. When it dawned on the passengers that they were gliding toward the ground, it grew quiet on the plane. No panic, only silent prayer. Captain Chesley Sullenberger called air traffic control: “Hit birds. We’ve lost thrust in both engines. We’re turning back towards LaGuardia.” But landing short of the airport would have catastrophic consequences, for passengers, crew, and the people living below. The captain and the copilot had to make a good judgment. Could the plane actually make it to LaGuardia, or would they have to try something more risky, such as a water landing in the Hudson River? One might expect the pilots to have measured speed, wind, altitude, and distance and fed this information into a calculator. Instead, they simply used a rule of thumb:

Fix your gaze on the tower: If the tower rises in your windshield, you won’t make it.

No estimation of the trajectory of the gliding plane is necessary. No time is wasted. And the rule is immune to calculation errors. In the words of copilot Jeffrey Skiles: “It’s not so much a mathematical calculation as visual, in that when you are flying in an airplane, things that—a point that you can’t reach will actually rise in your windshield. A point that you are going to overfly will descend in your windshield.”This time the point they were trying to reach did not descend but rose. They went for the Hudson.

Ok, we are done with planes. Now to another less scary example, how to do estimations? There is a principle called the Fermi problme. I will let Jason Cohen explain in his article Fermi ROI: Fixing the ROI rubric

The first full-scale nuclear bomb was detonated at 5:29am, July 16, 1945, in the New Mexican desert of the United States. The physicists who invented it were huddled in a truck behind a plate of welder’s glass to reduce the radiation to non-lethal levels.

The physicists were already causing trouble. Future Nobel Prize-winner Richard Feynman inexplicably decided to observe the blast without eye protection, causing frightening but ultimately temporary blindness. Current Nobel Prize-winner Enrico Fermi had taken bets with military guards about how much of the atmosphere would ignite, and whether it would incinerate the entire state or the entire world; some of the guards asked to be excused from the base, angering the project director.

Fermi was also interested in the amount of energy released by the blast—one of the main goals of the test. Not wanting to wait for official analysis, he made his own estimate on the spot, using a technique that now bears his name, and that we will use to fix our rubric:

About 40 seconds after the explosion the air blast reached me. I tried to estimate its strength by dropping from about six feet small pieces of paper before, during, and after the passage of the blast wave. Since, at the time, there was no wind I could observe very distinctly and actually measure the displacement of the pieces of paper that were in the process of falling while the blast was passing. The shift was about 2 1/2 meters, which, at the time, I estimated to correspond to the blast that would be produced by 10,000 tons of TNT.
—Enrico Fermi, Top Secret interview July 16, 1945, declassified in 1965

The official estimate of the energy output of the blast was 21,000 tons of TNT. Fermi’s estimate was surprisingly accurate given such inaccurate input data and quick, simple, mental calculations. How did he do it?

The trick—useful everywhere in life—is to estimate values using only orders-of-magnitude, a.k.a. powers-of-ten. No “low/high ranges,” no precision, not even any digits other than a 1 followed by a quantity of 0s. It sounds far too imprecise to be practical, and yet Fermi’s bits of paper demonstrate that it just might work.

Why Should We Use Simple Rules Most of the Time?

When making decisions there are three considerations we take into account; is this decision reversible? Does accuracy matter? And is it time-sensitive?

My argument is that the only instances in which simple rules are not the best solution are cases in which accuracy matters, the decision is irreversible, and we are not pressed on time. For example, deciding to do a non-urgent yet life-threatening surgery is worth mulling over. Actually applying simple rules here might be irresponsible.

For any other situation, simple rules are always the best path. If the situation requires making a decision fast then by definition you can’t think it through and in most cases, winging it is not really a good way of making decisions.

Where to Go from Here?

There is more to talk about when it comes to simple rules. I will not get into it here, I will probably write about it in other posts.

I will leave you with this, the mindset to apply simple rules is that you should abandon any desire for perfection. Then you need to convince yourself that for most problems there are no more than 5-6 things that actually matter (6 is somewhat pushing it). You combine these two ideas and then go find a problem you deal with often and figure out what matters and what are the rules that, if applied, will ensure what really matters is being taken care of.