Recently, in reviewing an academic article, I came across the following sentence in the notes to a table:
“Industry and year-specific intercepts are not included for brevity.”
At first glance, the meaning might seem obvious, but let’s look again. Are you including the intercepts or not? Because this could mean two things: that the intercepts are there not for brevity but for completeness, OR that in an effort to be brief, the intercepts have been left out.
The Chicago Manual of Style (17th edition) addresses this in section 6.31:
A dependent clause that follows a main clause should not be preceded by a comma if it is restrictive, that is, essential to the meaning of the main clause. For instance, in the first example below, it is not necessarily true that “we will agree to the proposal”; it is, however, true that “we will agree” to it “if you accept our conditions.”
We will agree to the proposal if you accept our conditions.
Paul was astonished when he heard the terms.
He wasn’t running because he was afraid; he was running because he was late.
If the dependent clause is merely supplementary or parenthetical, it should be preceded by a comma. Such distinctions are occasionally tenuous. In fact, as the third example below makes clear, the meaning in such cases can depend entirely on the presence or absence of a comma (compare with the third example above). If in doubt, rephrase.
I’d like the tom yum, if you don’t mind.
At last she arrived, when the food was cold.
He didn’t run, because he was afraid to move.
or
Because he was afraid to move, he didn’t run.
CMOS 17, 6.31 “Comma following main clause”
Bottom line: we include the comma for clarity. For clarity, we include the comma. We do not include the comma for frivolity, we include it for clarity.
Do you see what I did there?
While we’re on the topic of clarity, let’s look at the hyphen. “[Y]ear-specific intercepts” is clear enough, but are we talking about industry intercepts or industry-specific intercepts? An expert in the field may find this laughable and the answer obvious, but for the sake of clarity, if we are talking about industry-specific intercepts, we would need what Chicago 17 calls the “suspended hyphen” (section 7.88): “industry- and year-specific intercepts”.
Put that all together, and the diamond-clear sentence looks like this:
For brevity, industry- and year-specific intercepts are not included.
As a proofreader, it would technically be my job to only flag this to the publisher, but not to mark it for correction. As a copy editor, I would fix it because the assigned style guide backs me up in both cases. Depending on the publication process and my relationship with the managing editor, as a proofreader I may have room to make a judgement call.
But yes, I am one of those rare breeds who thinks this stuff is fun, and fascinating. And sometimes, a missing comma can have big consequences, so it’s worth it to have someone around who notices these things.