Hello and thanks for downloading the more or less podcast. I'm Nathan Gower.

We're the programme that thinks you only really understand the world by looking at it through numbers.

And there are no shortage of those in what we're discussing today, stock markets.

These are where shares in publicly listed companies are bought and sold, and where fortunes are made and lost.

In recent months, stock markets have been a hot topic, as fevered excitement about the potential

of artificial intelligence has driven the value of tech companies ever higher.

Senior figures in global finance, from the CEO of J.P. Morgan Chase to the governor of the

Bank of England, have been expressing worries in recent weeks.

Even the boss of Google has said the AI investment boom

has elements of irrationality. So is this rise unsustainable, a so-called bubble that might go pop?

It's a question our loyal listeners are asking, like Yanny.

My social media circles often characterize the AI boom as a bubble. I'd love to hear a more or less take on this. Can we identify economic bubbles before they burst? And does the current AI fad qualify as one?

An excellent question, Yanni. Well, last month, we spoke to some experts in financial markets for another BBC podcast, the briefing room, and they had a go at answering this exact question.

First up, Simon French, chief economist at the investment company Panmure Libarum. Just how big is the recent rise in the value of the stock market?

The rebound in global stock markets, led by the US stock market, has added about

$28 trillion to the value of global shares. Now, to put that number in context, that's almost

the size of the US economic output each year. And

that's a 31% increase in just six months since the global stock markets bottomed out after

Liberation Day in the US. And that has only happened on three previous occasions in modern

market history. 1987, 1999 and 2009.

Now, just in case you haven't been playing the stock market for the last 40 years,

let's recap,

...