Which businesses are the least transparent?

July 11, 2012, 10:51 AM UTC

FORTUNE — Big Energy is the most “transparent” industry when it comes to corruption-fighting, according to Transparency International, a global anti-corruption watchdog.

The might sound surprising. But those who prefer predictability can take heart in the fact that the finance sector is the least transparent, says the group’s latest report, issued on Tuesday. That result is weighted by the fact that four of the “least transparent” companies on the overall list are Chinese banks. But the organization says that, nevertheless, “the remaining financial companies were also below average.”

On a scale of 0-10, the finance sector averaged a score of just 4.2. The organization examined the world’s largest 105 companies. Only two-thirds of them voluntarily report on their corruption-prevention policies, but that’s better than the last time Transparency International issued a report, in 2009, when less than half of them did.

Only 78 of the 105 fully disclosed information about where all their corporate subsidiaries were registered. That makes it “difficult to know how operations in locations such as developing countries or secrecy jurisdictions [tax havens] feature in company earnings,” the report states. Many companies on the list also do not report what taxes they pay in foreign jurisdictions.

Why did the oil and gas sector score so high? “Hopefully, it’s a sign that pressure from investors, governments, and society encourages businesses to become more transparent,” according to the report. Companies in that sector “have long been targeted for the opacity of their operations, but have improved noticeably in this regard since Transparency International first evaluated them in 2008.”

One outlier is Russia’s state-controlled Gazprom, the largest extractor of natural gas in the world and Russia’s largest company. It scored just a 2.8. Still, that’s better than Berkshire Hathaway (BRK.A), which scored only 2.4. And it’s on a par with Amazon’s (AMZN) 2.8. Indeed, the tech/Internet sector in general doesn’t fare well in the findings. Apple (AAPL) scored 3.2 and Verizon (VZ) 3.3. This might be yet another area where tech is given something of a pass.

Topping the list was Norway’s Statoil (STO), which got a score of 8.3.