What could China and America’s clash at the G20 mean for your money?

If there's any clearer sign that politics actually matters again to investors, it's the fact that anyone gives two hoots about a G20 conference.

Not so long ago, G20 meetings were about as interesting as a council meeting in your local town hall, and a lot less relevant to your day-to-day life.

Now markets are waiting with bated breath as leaders of the world's biggest economies specifically two of them sit down over fine Argentinian steak, to talk shop.

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So come Monday morning, once the Malbec's all been drained (not by Trump, obviously) and the first-class flights have departed Buenos Aires en masse, what should we be looking out for, and what might be the impact on your portfolio?

What's on the table at the G20

There are lots of issues on the table in Argentina this weekend, in a two-day G20 summit that starts today. There's all the usual stuff that the bigwigs pretend to pay attention to, like climate change.

There's the small matter of Saudi Arabia blatantly murdering a high-profile journalist. There's the other small matter of Russia blatantly increasing its aggression in Ukraine (and, in case we haven't forgotten, killing people on British soil).

But the core of this summit in terms of what may or may not matter from a market point of view lies China's trade relationship with the US. So all eyes are on US president Donald Trump, and Chinese president Xi Jinping.

At the moment, the US has already imposed tariffs of 10% on $200bn of Chinese goods (a bit less than half of total imports). He plans to impose even higher tariffs 25% on that $200bn from early next year. He has made it clear that he's quite keen to slap tariffs on the remaining $267bn as well.

Trump, as I've often said, has a point. China does not play fair on trade. Whether you think that's reasonable or not (historically, mercantilism has been the way for lots of countries to get ahead in the world) is beside the point. No one denies that China has a history of pinching intellectual property.

But of course, no one is really all that keen to see a trade war either. Globalisation and outsourcing and all the rest of it have lowered costs for companies and consumers around the world.

The side effects have not always been brilliant for certain groups of workers (which is one reason we have the current political atmosphere). But from an investment point of view, a reduction in trade would probably hit corporate profits, and drive up inflation (and potentially interest rates).

There's also the more worrying issue of the world's key superpower and its key burgeoning superpower being at loggerheads. There is plenty of tension between China and the US already, and the risk is that trade tension turns into something more physical.

Plenty of people are talking about the "Thucydides trap", which is the idea that when you have a rising power it's very hard for it to avoid conflict with the incumbent power. (Thucydides wrote about the Peloponnesian War, where Sparta the incumbent battled Athens the challenger.)

It's all about the psychology. The rising power rattles the incumbent. Neither of them feels as though they can lose face to the other. So you get increasing hostility, misunderstandings, and brinksmanship. A big multinational game of chicken, basically.

War is, of course, not inevitable. It's fun for commenters and academics to toss around learned-sounding catchphrases like "Thucydides trap" around, but real life is more complicated. But it's certainly something to be aware of.

The world's problems are unlikely to be solved over a steak dinner

So what's likely to come out of the summit?

Honestly? It's just another talking shop. What do you think will come out of it?

You think these two guys will sit down for a steak dinner and hammer out the US-China relationship in an evening? Of course you don't.

However, this is another trigger point for a potential rally in markets.

Markets are primed to react to good news. They want excuses to go up at the moment. They're not enjoying this bout of nerves. They felt a lot better once the Federal Reserve came back onside this week, and they'd like it a whole lot more if it looked as though China and America's relationship was going to simmer down for a bit.

So it's all in the tone of the compromise that comes out of the discussion. And as John Authers points out on Bloomberg, "in the short term, the trade issue is technical and complicated enough that it shouldn't be difficult to come up with a fudge that allows Trump to claim victory without raising tariffs to 25% next year."

In other words, unless something goes really badly wrong on Saturday, you'd expect some anodyne platitude that can be interpreted positively by anyone who wants an excuse to push markets higher come Monday.

In the longer run, this is more about China's economy than about America's. China has backed itself into a corner to an extent. I would expect the internal economic pressure that's building to come out in the form of an even weaker currency, but that's a story for next year and beyond.

Just before I go this morning, we've just put up a new podcast in which Merryn and I discuss Brexit and Theresa May's deal. We've massively improved the sound quality too so don't miss it, it's only 15 minutes long.