The 85% Rule: What the 1918 Study Actually Found

You know the drill. You spend years mastering your stack, keeping up with the latest frameworks, and making sure your code is airtight. You're good at what you do.

But when it comes to landing that next senior role or getting a project off the ground, the technical chops only get you in the room. What keeps you there? Being someone people actually want to work with.

That idea usually arrives with a number attached: 85% of success is "human engineering", only 15% is technical knowledge, according to "the Carnegie Institute". It's a good line. It just isn't what the research says.

Where the 85% comes from

The best-known version is in Dale Carnegie's 1936 bestseller, How to Win Friends and Influence People. He writes that even in engineering, about 15% of financial success is due to technical knowledge and about 85% to skill in human engineering, and credits investigations made under the Carnegie Foundation for the Advancement of Teaching.

The Carnegie Foundation has answered the question itself. Its FAQ says the figures were "extrapolated" from A Study of Engineering Education, a 1918 report by Charles Riborg Mann, from the data on pages 106 and 107 (Carnegie Foundation). So I read those pages.

What the 1918 report actually says

Mann's report was written for a committee of American engineering societies, to work out what engineering schools should teach. Part of it asked engineers what decides success in their profession (Mann, 1918, chapter 16). It did that in two rounds.

• Fifteen hundred engineers answered, in writing, "What are the most important factors in determining probable success or failure in engineering?" They mentioned personal qualities more than seven times as often as engineering knowledge and technique.
• A second letter went to the 30,000 members of four engineering societies, asking each to rank six groups of qualities: Character, Judgment, Efficiency, Understanding of men, Knowledge and Technique. More than 7,000 replied. Character came first by a majority of 94.5%, and Technique came last.

There is no 85% and no 15% in it, and nothing about money. It's an opinion survey of American engineers, more than a century ago, about what they valued when judging success and sizing up young engineers for jobs and promotion. Nobody measured anyone's career. And the personal qualities the engineers had in mind weren't charm: the report lists common sense, integrity, resourcefulness, initiative, tact, thoroughness, accuracy, efficiency and understanding of men.

So is the rule wrong?

The number is. The idea behind it held up well enough that thousands of engineers put character, judgment and understanding of people ahead of technique. Being good with people isn't a soft extra, even in a technical job.

Think about the last time you really hit it off with someone at a meetup. It wasn't because you debated the finer points of system architecture.

It was because they remembered you were spending your weekends building a wooden dining table from scratch, or that you were planning a long-distance cycling trip from Brisbane to Sydney, and they actually asked you about it.

Remembering is the part you can practise

Remembering the small things shows you were actually listening. It bridges the gap between a sterile "networking contact" and an actual mate.

But keeping track of everyone's hobbies, weekend projects, and kids' names is a lot to hold in your head.

You don't need to force yourself to remember it all, and you don't need a spreadsheet you'll never open. When you walk away from a good chat, open OldMate, tap record, and speak while the details are still fresh.

"Met Marcus. Good guy, looking for a senior software engineer role. Spends his weekends painting with acrylics."

OldMate sorts the useful context into relationship memory. Next time you see Marcus, find him by name and get back up to speed. You can skip the awkward re-introduction and pick up the conversation with care.