Premise

It’s a good question: what’s the limit for deciding when a source is “too old” to use in your research? Some experts will tell you that the cut off is five years; others will say ten; and some might even say more. So which is right? And why?

In general, these guidances can be useful, but they are just that: guidances. I.e., they’re not necessarily hard rules, but rather, guidelines to consider. So what are these considerations, and why do they change on a case-by-case basis?

Examples

Stuff That’s Definitely Too Old

Let’s say that you’re writing a paper on climate change and you find what seems like a credible source. It’s a study in a prestigious science journal, authored by professionals with fancy doctoral titles pinned next to their names. Looks great! But lo and behold, as you’re working to copy some key quotes from the text, you realize that the study was actually published thirty years ago.

So why is this a problem? In this case (since it’s a science topic) it’s likely that a lot has changed in the past several decades. Whether the study’s content (e.g., the climate) or the tools and science used at the time, it’s possible (and sometimes likely) that their findings, conclusions, assertions, etc. might be outdated. And if you can corroborate that they are correct by cross-referencing them with much more recent scientific studies, then why not just cite those later sources instead? The answer: you would.

There’s a caveat here, however. You could, for example, reference our original example in your work in order to highlight a particular point of commentary, such as:

• Hey, look! These findings from thirty years ago are the same as they are today. Therefore, we can say with even more confidence that this issue has existed for a long time, so we should definitely do something about it as the science has shown this truth for decades.
• Hey, look! These findings from thirty years ago are so different than they are today. It’s important, therefore, to continue researching this topic to learn even more about the true complexity behind the issue.

Stuff That’s Probably Too Recent

Many are surprised to hear that some researched sources can sometimes be too recent to use in their work. Well, that’s not entirely accurate. It’s more about how you use these “too recent” sources that can be a problem.

Imagine, for example, that you’re writing a research paper several years ago, and your professor tells you that “valid sources are those that are within the past five years.” But you are researching about COVID and the year is 2021. The good news is that you’ll find few if any researched resources about COVID that are older than five years because, well, it wasn’t really much of a “thing” before the global pandemic.

(We actually checked in one of the largest global medical databases, btw, and there was literally one result for the search term “covid” from the year 2018. But there were hundreds of thousands in the subsequent few years.)

But the bad news is that even the initial flood of studies starting in 2020 themselves might already be too old—even though they’re only from a year ago. This is due to the recency of the topic, issue, etc. In fact, if you read the descriptions of these studies from this timeframe, plenty will mention that their findings are not necessarily conclusive and that more research desperately needs to be done to reach a consensus.

So, it’s not so much that you can’t use these sources; it’s just that you need to consider the context of their timeframes as part of your analytical considerations of resources—and your commentary.

Further Considerations

• Remember that nothing exists in a vacuum. That’s just a fancy way of saying that you have to consider the factors mentioned above before just declaring that a source is either “too old” or “too new.”
• Often not conclusive. Keep in mind—as also mentioned above—that lots of research studies themselves will explicitly state in their own findings (and especially abstracts) how much, and to what potential degree(s), that elements within their work need to be investigated further in order for more conclusive claims to be asserted with greater confidence.
• Consider using the studies themselves for research. You’d be surprised how often researched findings cite dozens—if not hundreds—of researched studies themselves. As such, they’re worth taking a gander at as they can often cite more recent or older information that you might want to reference for the reasons we discussed earlier. Check your sources own citation pages!