An educated adjective

Yesterday I saw a letter (from someone smart enough to know better) that included the phrase "an educated populous." An educated populace ought to know the difference between populous (an adjective) and populace (a noun), even though they are indistinguishable when spoken: A populous city has a large populace. See? Easy.

More writers might be aware of the distinction if the words were used more frequently in writing, but the Google N-Gram Viewer indicates that the use of the words in books has declined steadily in the past two centuries

Of course, both words appear in such a teeny percentage of printed texts that the difference is not as dramatic as it might look. And of course this chart does not indicate whether the words are used correctly; for that, let's see how many times these phrases appear in a basic Google search:

an educated populous: 33,300 hits
an educated populace: 505,000 hits

So the general populace seems to be getting it right most of the time, but those 33,300 hits disturb me. Who are these people? The first hit led to an article with the phrase an educated populace in the title, so why did it show up at the top of the list for an educated populous?

Then I looked at the web address. Bingo: an educated populous was part of the url. Who got it wrong: the original author, the headline writer, or the tech person?

Many of the hits under "an educated populous" came from blogs, which is not surprising (and new searches will lead to this one as well!), but I was a little surprised to see an educated populous in this official statement on the site of a teachers' association: "Public education benefits all of us, from the children whose lives it enriches, to the rest of us, who, though out of school, reap the benefits of an educated populous."

Except for those whose education fails to introduce the difference between populous and populace. Time to go reap some more benefits of education, people! Let's not be part of the 33,300!