Philip Jacob

The Root Cause

· Philip Jacob

Friday, NYC – the end of a long week. A young couple arrives home from work to their apartment. The main characters of this story, Alice and Bob, have decided to spend a quiet evening together, cook dinner and watch a movie. They walk to the grocery store near their apartment and begin walking through the aisles, putting rice, fish, carrots, etc. into their shopping basket.

Bob is occupied constantly with his phone, which Alice is aware of. Bob is receiving messages from his colleagues at work in another timezone who have some urgent questions for him. He is annoyed that his colleagues didn’t ask their questions earlier in the day. He even had held a meeting with them that very morning to clear up any loose ends precisely to avoid the situation he now finds himself in – having to respond to their questions off-hours. Nevertheless, he feels obligated to spend a few minutes responding to their messages in order to save his colleagues from their confusion and to save himself from having to fix their mistakes on Monday.

When our couple arrives at the checkout line, Alice begins unloading the groceries from their basket. Bob is still on his phone responding to messages, but he is aware that Alice’s patience is running thin and that he needs to wind this up. As the cashier scans the grocery products, Bob is hoping that she will also put them into bags. However, the supermarket is busy and the cashier makes no indication that she will assist with the grocery bagging. She scans each item and pushes it along.

With some frustration, Bob slides past Alice to the end of the conveyor and starts to bag the groceries. Bob’s phone is again delivering notifications so Bob takes a quick look, only to realize Alice is staring at him. Bob quickly takes out a single bag and begins putting all the groceries into it. Alice notices that Bob has not double bagged the groceries and is concerned about the bottle of wine and the carton of eggs, both of which are heavy. She says nothing, however, because Bob is prone to overreacting to perceived criticism and she doesn’t want to risk ruining their evening.

The cashier also notices that Bob has single bagged the groceries and is overloading the bag. However, her shift ends in fifteen minutes and she couldn’t be bothered. Earlier in the day, the cashier was notified by her manager that her hours will be reduced from 18 hours per week to 15 hours per week in support of a cost cutting initiative. She feels lucky that her position wasn’t eliminated entirely, but, still, she wonders if the loss of income from her reduced hours is enough of a reason to look for another position. Nonetheless, she is feeling pretty deflated and just wants to finish her shift and go home.

Bob continues putting the groceries into the bag. What Bob doesn’t know is that the single bag he has overloaded is less strong than what he is accustomed to. Just this week, the supermarket chain switched from their longtime standard bags with a grammage of 120 gr. / m^2 to 90 gr. / m^2 in order to save costs. Lighter bags cost less because they use less raw material and they also cost less to ship in bulk. The purchasing manager who noticed this cost saving opportunity received a congratulatory email from their longtime head of finance a few weeks ago. The purchasing manager recently joined the supermarket chain’s head office after an 18 year career running purchasing for a wholesale automotive supply. Their lack of experience in the supermarket business was not a factor, because, well, purchasing is pretty much the same across industries.

Alice pays the cashier. The cashier raises her eyebrows at the overloaded bag as she drops the printed receipt into it. Alice notices the cashier’s facial expression. Bob is again on his phone responding to his colleagues. There’s a long line of shoppers waiting to check out, so Bob picks up the bag and walks outside with Alice.

No sooner than reaching the end of the block does the bag rip. The bottle of wine falls out and cracks, splashing wine all over Bob’s trousers. The eggs quickly follow along with everything else in the bag.

This is the incident.


When something goes wrong, many people like to talk about finding the root cause. Which of the following factors is the Root Cause of this incident? Remember, there can only be one root cause:

  • Bob put too many groceries into the bag
  • Alice noticed that Bob overloaded the bag but didn’t say anything
  • The cashier noticed that Bob overloaded the bag but didn’t say anything
  • Bob was preoccupied with work and failed to handle his emotional state
  • Bob’s colleagues were distracting him
  • Bob’s colleagues didn’t ask their questions during the meeting Bob organized
  • The cashier’s manager made her feel demotivated to care about customers
  • The purchasing manager failed to consider the customer impact of weaker bags
  • The experienced finance manager failed to flag the risk of weaker bags to the purchasing manager
  • Bob and Alice failed to work on their communication skills which makes it hard to communicate sometimes
  • Alice has not overcome her fear of upsetting Bob
  • The manufacturer of the bags failed to document the decreased tensile strength to the purchasing manager of the supermarket chain
  • Bob failed to react quickly enough to the falling ingredients

Maybe one factor jumps out to you as the rootiest root cause, but I can guarantee you that building consensus on a single root cause with a group of people is harder than it looks. Everyone has their own perspective. One frequent failure mode of putting pressure on really trying to nail down a root cause is that the discussion frequently becomes more and more abstract. Eventually, if you push hard on finding the ultimate root cause, you can elect to hold the CEO responsible for not fostering a culture of excellence for nearly every incident that happens. I don’t find that particularly helpful.

The reason I don’t find the root cause model helpful in incident analysis is because it gets in the way of learning. In the short story above, there are many opportunities for all parties involved to learn something about how they can better participate in this small system. Adapting based on learning may require more work for some participants, but the point is that a person involved should be able to find some way to improve the system based on the factors they can control or influence.

A better model is one that relies on two simple concepts: the trigger and contributing factors. In the short story above, the trigger is simple: the groceries fell on the ground and were ruined. The contributing factors, as you can guess, are all the items in the list above. Notice that this model doesn’t involve getting stuck in a cycle of asking why did Thing #1 happen and, oh, what caused that to happen and, oh, that was Thing #2. Was Bob’s failure to double-bag the root cause? Well, no, because, while he did make that mistake, didn’t both the cashier and Alice notice it and fail to prevent the incident? Yes, but if the cashier wasn’t demotivated, maybe she would have helped the customer bag the groceries. And on it goes. Establishing a root cause in a complex system is a valueless exercise.

And, let’s face it, everything exists in a complex system. If any of the contributing factors above had not happened, the incident itself simply may not have occurred. You can pretty much assume that complex incidents necessarily involve multiple co-occurring factors that play a part in the unintended outcome. The collusion of these mostly independent factors is the interesting part. When they occur in isolation, they typically don’t present a problem; when they co-occur, that’s when things go wrong. You can think of this as an opportunity to learn. And I don’t mean that in a positive corp-speak kind of way. Each party in the system has an opportunity to gain a new perspective that can result in a behavior change or another adaptation that will enable them to build resilience into the system by changing the factors they control.

To belabor the point, the reason why the new perspective is invaluable is that our incident review conversation can happen without focusing on the pointless endeavor of chasing a root cause and instead focus on finding ways to learn. If we learn, we can adapt. If we can adapt, we can drive better outcomes.