I'm a journalist and a writer,

and my new book is called “Collusion,” and it's about Donald Trump and Russia.

Putin and money, they're a taboo topic inside Russia.

I wrote stories about this in 2007 based on sources inside his presidential administration who were saying, quietly,

that he was worth about $40 billion.

That was a decade ago.

The thing is Russia's a kleptocracy.

It's also the world's biggest oil producer,

and the people at the top of the Russian state are all kind of multi-billionaires.

And Putin is at the head of this pyramid although officially his salary's $100 thousand a year.

Putin allegedly controls 37% of Russian oil company Surgutneftegaz, 4.5% of natural gas company Gazprom.

He also has holdings in commodities trader Gunvor.

In 2012, estimates of his wealth were upped to $70 billion.

Now, everyone in the Russian elite knows he's the richest guy in town by a long way,

but the beauty of the system is that formally nothing belongs to him and everything is held by proxies,

some of whom are now under US sanctions.

It's a kind of clever system,

but of course he's enormously rich and for Putin,

the thing about money is it's kind of liquid power, and power ultimately is what interests him.