Nothing Works Alone
Touch traffic, and you affect air quality. Improve air quality, and you improve public health. Redesign streets, and you enable integration. Everything connected to everything else.
This is the final article in this series, and it is about the thing that connects the previous five.
Each article described a pattern — a specific way that intelligent, well-intentioned people get complex problems wrong. Treating symptoms instead of causes. Counting what is visible instead of what matters. Trusting single metrics. Responding to perceived risk instead of measured risk. Solving problems in silos.
These patterns are not independent. They are a system.
When Modena's traffic engineers add road capacity, they are treating the symptom. When the air quality barely improves after traffic disappears, it is because the invisible sources — heating, agriculture, atmospheric chemistry — were never counted. When the recycling rate looks good at 78.9% but the true material recovery is far lower, the single number is hiding the system. When a shop owner closes early because the street feels unsafe in a city with a homicide rate of 0.6 per 100,000, the mirage is operating. And when the engineer who can fix the canal spends twelve years navigating five institutions, the silo is the root cause.
Each pattern reinforces the others. The symptom bias makes the invisible stay invisible. The single number enables the silo by giving each department a metric to optimise in isolation. The mirage diverts attention and resources from the structural risks to the dramatic ones. They are not six problems. They are one system of thinking errors.
DMAIC was designed for production lines. But the logic is universal. Define the real problem. Measure what matters. Analyse the root cause. Improve the system, not the symptom. Control — make it last beyond the next election, the next budget cycle, the next administration.
That last phase — Control — might be the most neglected of all. Beijing's emergency measures during the 2008 Olympics dropped PM2.5 by 30%. The effects disappeared within a year. Delhi's odd-even vehicle scheme cut PM2.5 by 10–13%. Mexico City's Hoy No Circula programme, introduced in 1989, led residents to buy second cars to circumvent the restrictions. Italy's working-age population is projected to decline by 7.7 million by 2050 according to ISTAT — meaning every system built today must be designed to survive demographic transformation, not just the current political cycle.
The method works. The evidence is there. What is usually missing is the discipline to apply all five phases, in order, without skipping the uncomfortable ones.
I wrote a book about this. It uses one city — Modena — as the investigation, and a corgi from outer space as the narrator. Every character is fictional. Every number is real.
It is called Statistics Don't Cough: Six Problems, One City, One Corgi, and it will be available soon.
