> I wonder where the opposite fact that I hear on the internet that most olive oil is adulterated comes from.

I think it might come from conflating two different issues. Most EVOO in the US is "legit" - it actually is EVOO, although there are exceptions. On the other hand, a whole bunch of EVOO is "low quality", or more precisely, rancid. I've even heard that it's so common that Americans have come to prefer the taste of rancid olive oil over fresh.

Here's an article on FiveThirtyEight that explains the connection between the two problems:

> You may have heard by now that the olive oil in your kitchen cupboard may be an impostor. After a 2010 report found that 69 percent of imported olive oil in the U.S. failed to meet international standards, thousands of news stories were published, often incorrectly describing the presence of “fake” olive oils in grocery stores. ... The hysteria recently led Congress to assign a new job to the the Food and Drug Administration: sampling imported olive oil to see whether it’s adulterated or fraudulently labeled. ... But there’s something that not even the mighty FDA can fix: most of us don’t know the difference between a high- and low-quality olive oil.

> Though there’s a long history of scandal in the olive oil world, the problem in the U.S. for consumers is less about oil that isn’t made from olives, and more about olive oil that doesn’t meet the quality standards declared on its label. But since most people in the U.S. can’t tell fusty and musty from pungent and fruity, low-quality olive oil masquerading as extra virgin is a hard problem to fix. ... “We call the U.S. the world’s dumping ground for rancid and defective olive oil. We don’t know the difference,” said Sue Langstaff ... Studies have shown that even frequent olive oil consumers in the U.S. don’t know what the extra virgin or cold pressed designations mean, let alone have the ability to taste the difference. And in blind taste tests, consumers often prefer lower-quality olive oils.

https://fivethirtyeight.com/features/most-of-us-are-blissful...

> I wonder where the opposite fact that I hear on the internet that most olive oil is adulterated comes from.

If someone on the internet is telling you something is bad, they probably got their information from someone else on the internet. The number of people willing to guess based on their gut feelings is too damn high. People don’t know what they’re talking about and letting everybody know how bad for you something is is a toxic infectious idea disease.

Where does it come from? I’m guessing in this case the trend of making a product like salad dressing that advertises its evoo content and neglects to mention it also contains a majority of cheaper oils unless you actually look at the ingredients.

Although there is still some amount of self-interest there (presumably the North American Olive Oil Association still indirectly benefits from increased olive oil consumption, even if it's not olive oil sold by one of its members), it's quite refreshing to see a certification organization straightforwardly assess the risk to consumers from getting a non-certified product with absolutely no waffling about. Too often certification organizations resort to FUD to play up the amount of danger in getting something without their stamp of approval.

I read several times 2 stories in the past 5 years: the exported quantity of olive oil in Italy is bigger than the entire country's production and the global sales of Motul engine oils is 3 to 5 times bigger than their production capacity. I am not 100% of these stories, but at the time I read these they were from multiple reputable sources.