Help me with my verb tenses...

have found

Firm-level survey data carried out by W and O in developing countries (2004) showed that the cost of complying with a foreign technical regulation was higher (etc).

Thanks for your input guys...

But I still don't understand what the difference between these 3 sentences (pulled from an established economics journal) is.

1) "The CIE study (2001) identified autos..."

2) "A, B, and C (2000) claim that combined 'US' exports and imports with Mexico..."

3) "Even on this basis, Gilbert finds small welfare gains for both the United States and Australia, which he ascribes to....(Gilbert 2003)

I can see that perhaps a case could be made for continuing circumstances and single events in the past, but it seems to me that this line is quite blurry, at least in these 3 sentences. (Mostly for sentences number 2 & 3. Am I missing something?

the study is something that happened in the past. the authors stand by their data though, so that's present-tense.

So, the sentence by W and O is past tense because it's referring to a specific study that was done, and not about any sort of assertions being made?

I think the present tense of "show" would do just as well in that example. The author quoted here might of course want to use the past tense to emphasise that the conclusion of W & O may no longer hold, although I think the tense of "was" is sufficient for this purpose.

That sentence has got a more serious problem, however -- it claims that W & O carried out some data. Where to? The dustbin?

I've observed (colloquially) that one tends to use "found" to emphasize the solidity of their conclusions, whereas "find" implies some level of tentativeness. I don't know from actual rules though.

Yes, "find" in the simple present tense can certainly have the meaning "perceive" or "feel". "Found" or "have found" do not ususally carry this connotation. This is to do with that particular word, though, and doesn't necessarily apply to other words.

The line's blurry beceause studies and other publications are stubborn little bastards, and whatever they said upon publication, they're more than likely still saying the same thing today. Kind of like events in narratives: in the end, Romeo dies present tense (and no matter how many times you read it, he'll continue to die) -- but it's just as apt to point out that at the end of the story, Juliet died, too.

I think the good part is that you get to pick one or the other to kind of put the information in context, and what you wind up doing is making some things ALIVE and other things DEAD. Past tense is good when you're outlining history, or the thing in question isn't your focus, or you want to imply that things have changed since the time of the text you're discussing -- it's history now, it's in the past, it's not a part of the current debate on the topic. Present tense is good for marshalling (recent) evidence, and suggesting that the authors still stand by what they said, and that it's at play in today's conversation -- or else, as with literature, kind of focusing in on something to imply that it's alive and at issue in your own discussion. Hence, I dunno:

"In 1994's Big Important Study, Author McAuthorson claimed that the sky was pink. But McAuthorson Sucks, another mid-90s study, tells a very different story."

The tenses make the first one dead and gone and bring the second one into the spotlight -- like "let's look at what this says, right now, because it's not a settled issue and that's why I'm preparing to talk about it."

German's got this covreed -- you switch over into the subjunctive I (which has the distancing effect of English subjunctive, only you're distancing by speaker, not by actual v. possible) and the problem solves itself.