What is an acceptable error rate for a copyeditor or proofreader?

Let me clarify: How many errors can an editor let stand?


Pulled that number out of the air. (Serious numbers below.)

But seriously, I’m human, you’re human… Only [the divine] is perfect. Errors happen, and the more errors that are in a manuscript to begin with, the more errors will remain.

Even teams of editors can’t guarantee a impeccable prose.

You can have good, fast, or cheap; never all three.

— Rosemary Shipton, Canadian Editor

Heck, I’ve picked up “polo bears” (for polar), “crystal movement of tectonic plates” (for crustal), and “replace with page 273, DO NOT have image” (for “OMG you’re fired”) in finished books.

Rule #2: Never open a book you have finished.

— Adrienne Montgomerie, tired human professional

As a child, I noticed that my copy of Alice in Wonderland repeated a line. (That may have been my first realization that someone has to CHECK books. I can still remember the colour of the room I was sitting in at that moment.) Even whole _teams_ of editors can let errors get through. We’re still human.

When I worked in the planning and documentation department for a small aircraft manufacturer, we were taking flack for the typos in our documents, so we started researching acceptable error rates. At the time, there wasn’t a lot of data out there. Data entry clerks had established acceptable rates at something like 98%, which seemed very high. They were dealing mostly with “transcription”, not generating original works or fixing errors in others’ work.

The EAC considers 80% to be an exceptional standard of editing, if we take their pass criteria for certified editing exams to be their benchmark.

The Baltimore Sun guy has said “no one ever notices how much you _corrected_!”

One prof in Hawaii has analyzed a lot of studies about human error rates, including ones that looked at professional proofreaders. They average about 91%. Turns out my fanciful number is closer to reality than editors might like to admit.

UPDATE March 2021: Also see Webster’s calculation of errors in their dictionary.


You can read more about error rates in editing, and leave a comment, over on the the now-defunct Copyediting blog.

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