David Kestenbaum

I recently had a brief conversation with Ronald Coase.

"I'm 101 at the moment," he told me. "I get older by the minute."

Iceland is a tiny nation in a big financial mess. It's still recovering from the aftermath of the 2008 global economic crisis, which caused a domestic banking collapse.

Its currency, the krona, is also in really bad shape. That's led Icelanders to pose an existential currency question: Should they abandon the krona?

One key problem is size. Iceland has about as many people as Staten Island, so there just aren't that many people on the planet who need to use the krona.

"There are more people using Disney dollars," says Arsaell Valfells, an Icelandic economist.

China's central bank is sitting on a giant pool of U.S. dollars. It's the world's biggest holder of foreign reserves, worth over $3 trillion at last count.

All that money has piled up because every year, China exports more than it imports; it runs a trade surplus.

There are lots of reasons for China's trade surplus. In the past few decades, China has built an amazing manufacturing ecosystem. It's become the factory to the world.

The streets of Beijing and Shanghai feel like an entrepreneurial free-for-all, full of mom-and-pop stores and street vendors selling snacks and cheap toys.

But when you pull back the curtain, you see a different picture: a country where the government still controls huge swaths of the economy.

When you're in China, there's a good chance you're doing business with the government every time you:

• make a call on your cellphone (the government owns the country's biggest cellphone network)