A policy of nationalizing chunks of an economy inevitably creates oligarchs who skim profits off the country’s natural resources.

As such, you won’t be surprised to learn that the largest energy companies in the world are owned and operated by governments, and they include: Saudi Aramco, Russian Gazprom, China National Petroleum Corp. (CNPC), National Iranian Oil Co., Petroleos de Venezuela, Brazil’s Petrobras and Malaysia’s Petronas. How they’re run varies wildly—as does where their wealth goes.

While we’ve all been inundated with the massive amount of press on the scandals engulfing Brazil’s Petrobras, there are a few that stand out for creating and maintaining some of the world’s most interesting and colorful political leaders, who have grown their wealth through holdings in state-run oil and gas in some cases, and through more direct means in other cases.

Four state-run oil wealth stories stand out in today’s world: Russia, Azerbaijan, Kazakhstan, Angola and Brunei.

Vladimir Putin, Russia

Estimates of Russian President Vladimir Putin’s wealth only comes in ranges because most of his wealth is hidden through offshore companies or under clandestine financial devices.

The lower end of the range sits at US$40 billion – a 2007 figure based on research by mid-level Kremlin advisor Stanislav Belkovsky, which he later said had grown to US$70 billion. At this level, Putin already stands among Forbes’ Top 10 rankings of the world’s richest billionaires, though the magazine commented in 2015 that it could not verify enough of his assets to put him on the list.

Earlier this week, the International Business Times said Putin’s fortune could be as much as $200 billion.

The majority of Putin’s wealth comes from his stakes in the oil sector. He is said to own 37 percent of Surgutneftegaz, 4.5 percent of Gazprom.

“At least $40 billion,” Belkovsy told the Guardian in 2007. “Maximum we cannot know. I suspect there are some businesses I know nothing about.”

Putin’s trophies of wealth are far from subtle. His $1 billion palace on the Black Sea features “a magnificent columned façade reminiscent of the country palaces Russian tsars built in the 18th century,” according to the BBC, which also procured evidence that a secret slush fund had been created by a group of oligarchs to build the estate for Putin, personally.