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'Decades of research has/have shown'

-decades is plural

-research is murky

I'd be inclined to write 'has'

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5 Answers 5

You only have one subject in your sentence: "decades of research".

Research modifies decades, but decades is definitely plural, so the correct sentence is

Decades of research have shown

The same is true the other way:

A line of cars is standing on the road. A bag of apples costs $2.

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While I would agree with your choice, it is not nearly so clear-cut as you imply. A google ngram on "years of reasearch have/has" shows "has" is less common than "have", but still running at half the incidence. Quantified expressions are tricky: " number of people have" is far more common than "a number of people has". –  Colin Fine Feb 26 at 10:43
"This bag of apples has worms in them," or "this bag of apples have worms in them"? Or do you have to rephrase it entirely because all the pluralities don't agree, and you can't say "this bag of apples has worms in it"? –  Peter Shor Feb 26 at 13:01
I would say and would have no problem understanding "This bag of apples has worms". Without specifying whether the apples or the bag contain or contains the worms (implicitly it is the bag in my version), I don't see a problem, as a bag with worms and apples is not more or less attractive depending on the worms being in the apples as well as in the bag. –  oerkelens Feb 26 at 13:09
@colinfine The danger of Ngrams is that it reports incorrect usages, too. –  David M Feb 26 at 13:37
@DavidM: The danger of "correct" is that it becomes divorced from what the language actually is. –  Colin Fine Feb 26 at 17:49

Looking at the actual usage stats from the Corpus of Contemporary American English, singular agreement in this construction is possible, but rather uncommon:

decades of research has      2
decades of research have    14
decades of [nn*] has         4
decades of [nn*] have       60
centuries of [nn*] has       2
centuries of [nn*] have     14
months of [nn*] has          7
months of [nn*] have        21

Looking at the British National Corpus, again both variants are not unheard of, but the corpus size is too small to say anything decisively:

decades of [nn*] has         1
decades of [nn*] have        0
centuries of [nn*] has       0
centuries of [nn*] have      3
months of [nn*] has          2
months of [nn*] have         3

In conclusion, when writing for an international audience, I would favor plural. When writing for a local audience, I would favor whatever comes more naturally to me in my local dialect.

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It depends on whether you're talking about the research or the decades. If you mean "Research which took decades", use the singular verb (research is a mass noun so it doesn't take plural verbs); if you mean "Decades, which were spent doing research", use the plural.

For example, "The decades of research were the happiest time of my life" but "Decades of research was needed to solve the problem." (Similarly, "tons of concrete was needed to fill the hole.")

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Adding to @oerkelens, research is almost irrelevant here because the the subject is 'Decades of x'

Decades of people

Decades of opinions

Decades of knowledge

It doesn't matter what there are decades of, have is still the appropriate word.

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What I do in these cases is ask: has the research shown, or have the decades shown. You could make a case for both, but the case for research is stronger. So I'd recommend:

Decades of research has shown ...

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If you want the research to show something, the sentence should be "after decades, research has show". Unless you would want to see this as a hypallage? –  oerkelens Feb 26 at 13:46
There is an admitted logical consistency to this. But, it sounds very foreign to my ear. –  David M Feb 26 at 13:49
Also, you could easily omit of research and maintain the meaning of the sentence. If you omit decades, the meaning shifts dramatically. –  David M Feb 26 at 13:50

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