Inside the 1987 NUMMI Management Practices Executive Summary: Why Leadership Mattered More Than Lean Tools

The blog post

In this episode, I explore the 1987 NUMMI Management Practices Executive Summary — a confidential General Motors report that documented why the joint venture between GM and Toyota was succeeding so dramatically.

What’s striking is how clearly GM’s own study team understood the real drivers of NUMMI’s performance. It wasn’t tools. It wasn’t discipline. It wasn’t copying Toyota’s production techniques.

It was leadership.

The report describes a management system built on mutual trust and respect, problem-solving at the source, quality built into the process, and supervisors acting as coaches rather than enforcers. Nearly 40 years ago, GM documented that NUMMI’s success came from management philosophy — not Lean tools.

And yet, insight proved easier than action.

In this episode, I walk through the document’s key sections, including NUMMI’s basic principles and five major management strategies, and reflect on why translating those lessons into broader cultural change proved so difficult.

If you’re interested in Lean leadership, psychological safety, or the origins of what we now call continuous improvement, this historical document offers powerful — and still relevant — lessons.