The two words “according to” act as a single preposition.
Although “according to” is always a preposition, it has more than one meaning.
You have to determine which meaning it has in a sentence before you know whether or not to put a comma before it.
Do you need a comma before “according to”?
You usually need a comma before “according to” when it means “stated by.” If “according to” is part of a very short phrase preceded by “that” or at the end of a sentence, the comma may be optional. “According to” should not be preceded by a comma when it means “in proportion to” or “contingent on.”
When “according to” means “stated by”
“According to” usually tells you who or what is passing on a piece of information. When it has this meaning, it can come at the beginning, the middle or the end of a sentence.
When “according to” has this meaning, it is usually part of a nonessential phrase or clause.
This means that it can be removed from the sentence without significantly changing its meaning or the structure.
A nonessential phrase or clause is supposed to be set apart from the rest of the sentence with commas, so usually there will be a comma before “according to” in these types of sentences.
It can be helpful to look at how “according to” as part of a nonessential phrase can move around in the same sentence and still be preceded by a comma:
The man was caught after robbing four houses, according to the police.
The man, according to police, was caught after robbing four houses.
The man was caught, according to police, after robbing four houses.
In each of the above sentences, the placement of “according to” helps to slightly emphasize a different part of the sentence.
In the first example, the emphasis is a little more on the fact that the man robbed four houses.
In the second, it is on the man himself, and in the third, it is on the fact that the man was caught.
However, in every sentence, it is part of a nonessential phrase, so it needs to be preceded by a comma.
“According to” as part of a nonessential phrase also often follows “that” in a sentence. Here’s an example:
That comma can be particularly important when “according to” is the beginning of a long dependent clause.
A sentence like the one below could be confusing without setting off the dependent clause with commas:
“According to” as part of a short phrase
It’s easy to simply remember the rule that when “according to” is used to attribute information to another person or thing, it needs to be preceded by a comma.
This can keep you from making errors in your writing.
However, you may sometimes see sentences that leave out the comma when “according to” is part of a very short phrase at the end of a sentence.
It can be helpful to know that you may sometimes see writers make this stylistic choice.
This gives the impression of a sentence that is spoken slightly faster:
This is also the case when “according to” follows “that”:
If “according to” is part of a short phrase in the middle of a sentence and is not preceded by “that,” the comma is usually necessary for clarity:
When “according to” means “in proportion to” or “contingent on”
Less commonly, “according to” indicates that one thing is proportionate to or contingent on another thing.
When this happens, you should never put a comma before “according to” because it always acts as part of an essential phrase.
Here is a sentence with and without that comma to illustrate the difference:
That little comma changes the meaning of “according to” in the sentence.
In the first example, the job descriptions of the workers says that they will be paid. This might be in contrast to a separate set of job descriptions for volunteer workers who are not paid.
In the second example, the lack of a comma tells us that “according to” means “contingent on.” Different workers will be paid different amounts based on what their job description is.
The example below is a less ambiguous one because the sentence would be nonsensical if you used a comma.
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