Investors have been throwing off their fears in regards to the state of the worldwide economic system and piling into high-flying US shares.

The benchmark S&P 500 index rallied on Thursday to shut at 4,293.93, up 20 % since its lows of early October, driving it into official bull market territory.

Performance has been pushed by buzz round synthetic intelligence (AI) and machine-learning expertise, which accountancy group PWC reckons will add greater than $15.7trillion (£12.5trillion) to the worldwide economic system by 2030.

This has triggered a clamour for the shares of mega-cap US expertise firms which can be prone to reap the advantages, notably chipmaker Nvidia.

Its shares have soared an unimaginable 170 % this yr, because the overwhelming majority of generative AI programmes practice utilizing its graphic processing models (GPUs).

Microsoft’s OpenGPT AI pure language processing chatbot is the quickest rising app of all time, described by Tesla's Elon Musk as "scary good". Users adore it and worry it in equal measure.

Microsoft's shares are hovering too, as are Apple, Amazon and Google-owner Alphabet, which has its personal chatbot referred to as Bard. Facebook-owner Meta Platforms and Tesla are rebounding after crashing in 2022.

Yet with out these seven market-thrashing surprise shares, the S&P 500 would even have fallen barely this yr.

Investors do not care, although. They are determined to purchase shares and earn cash once more, with CNN’s Fear and Greed Index hitting the “Extreme Greed” stage on Thursday.

This terrifies market analysts, who're urgently warning that as we speak is definitely a rotten time to purchase shares, as many are actually overvalued within the frenzy.

Today's bull market is constructed on a really skinny platform, and it might come crashing down at any time.

If it does, buyers who purchase at as we speak's dear ranges could possibly be plunged right into a world of ache.

Despite the tech frenzy, the US economic system is now heading in the direction of a recession, with Cristian Gattiker, chief business officer at Julius Baer, warning: “The US will likely cool off more than other countries after having been a growth stronghold.”

Axel Rudolph, senior market analyst at on-line buying and selling platform IG, warned that that is dangerous time to purchase shares as greed hits excessive ranges primarily based on only a handful of shares.

Victoria Scholar, head of funding at Interactive Investor warned: "Throwing money into the market right at the top is rarely a good idea.”

Investor sentiment has been boosted by successful extension of the US debt ceiling and hopes that the US Federal Reserve will freeze interest rates at its next meeting on June 14.

The Fed has increased lending rates every single month since March last year to 5.25 percent today.

Investors are desperate to see the Fed "pivot", the point at which it start cutting interest rates rather than hiking them. When that happens, today's bull market will really take off.

READ MORE: Next big stock market rally needs three things. Yesterday it got two of them

US inflation is falling but stood at 4.4 percent in April, more than double the Fed’s two percent target. That's almost half the UK's figure of 8.7 percent, though.

There is zero hope of the Bank of England freezing rates at its next meeting on June 22. Instead, it is expected to increase bank rate for the 13th time in a row to 4.75 percent.

Market consensus suggests UK base rates could soon hit 5.5 percent, which partly explains why the FTSE 100 isn't in a bull market.

High interest rates are bad for the economy because they drive up borrowing costs for consumers and businesses, and now risk triggering a UK home value crash.

It means savers can get up to 5.35 percent a year on cash with out risking their capital.

The FTSE 100 has grown steadily in current months, climbing 10.78% for the reason that lows of October 12, which is when the US bull market started.

Yet many analysts consider the US rally might be short-lived.

Matt Britzman, fairness analyst at Hargreaves Lansdown, says it has grown too quick with progress concentrated in only a few shares. “A pullback wouldn’t be too much of a surprise as markets take a breather.”

While the inventory market rally is nice news for pension and shares and shares Isa buyers, as we speak's excessive greed needs to be met with excessive warning.