It isn't. Some of their data has been suspect for a very long time, unfortunately (and ironically) there is also a partisan reason why the Economist doesn't mention the series that is most suspect: population estimates. These numbers are known bad for over two decades now...they have done nothing.
The US has had a far more serious approach to economic statistics, the ONS is a complete joke. It has never been easier or cheaper to collect stats but the ONS, for some series, is using collection methods that haven't changed since WW2. This is typical of government in the UK, completely isolated from the rest of society.
Complex systems are difficult to predict or reason about, especially in turbulent times, and when only partial information about the world is available, and only part of it is accurate. Nothing new under the sun. If you’d always know what’s going on, you could categorically beat the market or make central planning to work flawlessly.
This is a common misconception. A good understanding of economics might enable you to decide what kind of interventions to use (or to avoid) in an economy as a whole, but will not necessarily give you any insight into how well a particular company will do in the market. They are entirely different skills. As a very simple example, companies often fail for non–economic reasons such as fraud, negligence, incompetence, accidents, etc, etc.
Since we have allowed economic unions to become so huge that question is trivial to answer: huge unions concentrate wealth to an extreme extent. This is playing out both in the US and EU (slowly, or at least, slowly compared to the same playing out in China)
So which companies will do well? The already biggest ones, including the government itself. That's the only metric that matters, and this is indeed what we've seen since WW2.
S&P500 -> S&P100 -> FAANG -> MAG7 -> what do you think comes next? One, and only one, of the big 7 will win.
The problem is: everyone wants everything. The obvious "natural" fix is simple: go back to more power to smaller political entities. That will destroy large companies, as the smaller entities will change laws to make that happen, to protect themselves. Which means, no apple, no internet, no (significant amounts of) oil, no ... This is also ignoring that large entities will fight to defend themselves.
