For fifty years the Peter Principle was treated as one of those observations that make people smile but that nobody had really proven. Laurence J. Peter’s line — “in a hierarchy, every employee tends to rise to their level of incompetence” — circulated through MBA courses as provocation, not as data.
In recent years that has changed. Serious studies have come out, with large samples and rigorous methodologies. And the results confirm what many operations directors already suspected: internal promotion based on current performance systematically produces worse managers than other criteria would.
This article collects the three strongest empirical findings on the topic and translates them into concrete guidance for anyone running a fleet or an operational organization.
Finding #1: 53,035 salespeople, 214 firms, one disconcerting conclusion
The reference work is “Promotions and the Peter Principle,” published in the Quarterly Journal of Economics in 2020 by economists Alan Benson (University of Minnesota), Danielle Li (MIT), and Kelly Shue (Yale). The three accessed performance data on 53,035 salespeople across 214 American firms between 2005 and 2011. In the observed period, 1,531 of them were promoted to sales managers. The researchers could track their post-promotion managerial performance for years — something previous studies essentially couldn’t do.
Three key results:
Sales performance is a very strong predictor of promotion. All else equal, a salesperson who closed twice as many deals as a colleague was about 15% more likely to be promoted in a given month. Companies, openly or not, promote those who sell more.
Sales performance is negatively correlated with post-promotion managerial quality. Among the 1,531 promoted, those with higher pre-promotion sales became worse-than-average managers. More precisely: every doubling of pre-promotion sales performance was associated with a 7.5% drop in subordinate performance afterwards. The sign is the opposite of what efficient promotion would produce.
The aggregate cost is enormous. The three economists estimated that the firms observed would have achieved 30% better managerial performance had they promoted candidates selected at random from inside the same company. Thirty percent, applied to a sales or operations function of 200 people, is worth millions.
The operational takeaway is simple: individual performance is not the signal we thought it was. In fact, when it’s very high, it’s often a negative signal about the probability of managerial success.
Finding #2: 60% of those promoted fail
The second block of data comes from different sources — Corporate Executive Board, Chartered Management Institute (CMI), Center for Creative Leadership — and converges on numbers that have stayed surprisingly stable over time.
- About 60% of new managers fail in the first 12-24 months after promotion. “Fail” here means: removed from the role, resigned, or formally kept the role but with performance well below expectations.
- 82% reach the managerial role without any formal people-management training. These are the so-called “accidental managers”: people who become bosses because they were good at the previous job, not because they were prepared to lead a team.
- Among the most frequently cited causes of failure: difficulty delegating (47%), conflict management (41%), asymmetric communication with their own boss (38%), and time management (35%). All skills that are never tested before promotion.
These numbers matter especially for transport SMBs, where internal management training is almost non-existent and operational pressure leaves little room for structured onboarding into the role. The new fleet manager or new supervisor learns on the job — which, based on the data, means roughly a 60% probability of failure.
Finding #3: what actually works to reduce the damage
In 2025 a research group published on arXiv an agent-based model that simulates thousands of promotion scenarios, comparing four standard strategies (merit, seniority, hybrid 70/30, random) and two mitigation interventions (post-promotion training and selective demotion).
The results are illuminating.
Promoting for seniority is nearly worse than random. The idea that “those who’ve been here longest deserve to rise” produces managers on average less effective than purely random selection. The reason is statistical: seniority is not correlated with managerial skills, it’s simply a marker of company tenure. Rewarding loyalty is a legitimate choice, but it shouldn’t be confused with an effectiveness choice.
Merit-based promotion + post-promotion training recovers much of the gap. When the newly promoted receive structured management training in the first 90 days, the performance of their team improves significantly. It’s the simplest and most neglected antidote: don’t change the promotion criterion, but invest in the first three months that follow.
Timely selective demotion is a legitimate and functional tool. If within 6 months the team’s performance shows a significant drop (the study sets the threshold at -5%), bringing the manager back to the previous role — without financial penalty and with an active training path — is better for everyone: for subordinates, for the manager themselves, for the company. The problem is that in many corporate cultures this practice is almost taboo: perceived as humiliation rather than rational error management.
Operational translation: what changes for fleet leaders
The three blocks of evidence converge on four practical recommendations.
1. Stop treating individual performance as a signal of managerial potential. When you have to promote to supervisor, fleet manager, or coordinator, separate two assessments: who performs best in the current role, and who shows managerial skills (people management, reading aggregate data, communication). They overlap much less than they seem. The problem of the driver promoted to supervisor is the most frequent example in transport fleets.
2. Test before promoting. Giving the candidate a time-bound task that simulates the target role (managing an onboarding, owning a mini-project, coordinating a task force) costs little and tells you a lot. Companies that run this kind of assessment reduce post-promotion failures by about 30%, according to aggregate industry data.
3. Invest in the first 90 days after promotion, not just in selection. Structured management training, mentoring with a coordinator from another shift or department, weekly debrief with the direct manager. It’s the intervention with the best cost-benefit ratio there is. Given that the average cost of a bad managerial hire exceeds €15,000 per position (and in SMBs it can be a multiple, factoring in the impact on subordinates who resign), investing €2,000-3,000 in onboarding management training is almost always worth it.
4. Normalize the option of stepping back. A culture that rewards recognizing the mistake before letting it fester is a healthy culture. Timely demotion, handled with respect and without financial penalty, is rational management, not failure. Organizations that have introduced a formal stigma-free “step-back” path — present in some Anglo-Saxon groups — drastically reduce both subordinate turnover and manager turnover itself, since people often prefer to return to a role where they were effective rather than persist in a role where they suffer.
The Peter Principle is a system problem, not a people problem
The most common error in reading the Peter Principle is to treat it as an individual issue: “Marco wasn’t up to the job,” “the new fleet manager didn’t get the role.” It is instead, largely, a system problem: promotion criteria that reward the wrong thing, lack of career alternatives, absence of management training, taboos around revising decisions.
Recent empirical evidence has made the phenomenon measurable. Knowing that 60% of new managers fail, that individual performance is negatively correlated with managerial quality, that seniority is almost an anti-signal, should be enough to rethink how transport SMBs structure internal careers.
The data is there. Now what’s needed is the willingness to look at it.
For those who want to explore specific angles of this topic, our blog has an analysis of the seniority promotion trap in transport SMBs, a proposal for a specialist career track as an alternative to the management role, and a reflection on how AI and fleet software are changing the manager’s job — partly reducing the Peter Effect on coordination roles.