http://en.wikipedia.org/wiki/Olive_...nd_adulteration

adulterated olive oil has become the biggest source of agricultural fraud problems in the European Union.
While less than 10% of world olive oil production meets the criteria for labeling as extra-virgin, it has been estimated that up to 50% of retail oil is labeled "extra-virgin".
摻假的的橄欖油是歐盟最大的農業詐騙。
extra-virgin 產量只有 10%，但有 50% 的油標示為 extra-virgin。

In the United States, the Food and Drug Administration (FDA) doesn't routinely test imported olive oil for adulteration, and some products are difficult to test.
美國 FDA 對進口橄欖油沒做定期檢測。有些產品很難測試。

An article by Tom Mueller in the August 13, 2007 issue of The New Yorker states that major Italian shippers routinely adulterate olive oil and that only about 40% of olive oil sold as "extra virgin" actually meets the specification.

2007 年八月，美國進口的義大利 "extra virgin" 只有 40% 符合標示。

Under EU rules, olive oil may be sold as Italian even if it only contains a small amount of Italian oil.
照歐盟的規定，只要含有一小部份義大利油，就可以標示成義大利產的。

In March 2008, 400 Italian police officers conducted "Operation Golden Oil," arresting 23 people and confiscating 85 farms after an investigation revealed a large-scale scheme to relabel oils from other Mediterranean nations as Italian.

2008 三月，義大利抓到進口其它地中海國家的油再改標示的。

In April 2008, another operation impounded seven olive oil plants and arrested 40 people in nine provinces of northern and southern Italy for adding chlorophyll to sunflower and soybean oil and selling it as extra virgin olive oil, both in Italy and abroad. 25,000 liters of the fake oil were seized and prevented from being exported.

2008 四月，義大利就有用葉綠素加到沙拉油、葵花油的假造手法。而且是北義、南義
九個省份都有用這種手法。

In the first week of March 2010, researchers at the University of California at Davis' Olive Center purchased three bottles each of 14 imported olive oils and five California oils at retail stores in three different regions of California. Sixty-nine percent of the imported olive oils and 10% of the California oils failed to meet the IOC/USDA taste standards for extra-virgin olive oil.

2010 美國加州大學的測試， 69% 的進口油和 10% 的加州油都不符合 extra-virgin 的標準。

我就只截錄一部份，有興趣的還是看原文比較好。
當然這不代表政府就不用改進，
但是只有 10% 的 extra-virgin，
我很難相信台灣廠商會有穩定的貨源。