By Jamie Robertson BBC World business presenter

Perhaps the most surprising aspect of the turmoil of the last three weeks on the world's stock markets has been the relative stability of the world's biggest stocks.

Toyota was one of the biggest losers on the Global 30 in May

Certainly the Global 30 has shed some 5.8%, but within that, there were losers - and bad losers.

The bad losers were in Asia, where on average, the Global 30 shares lost 7.2%. Seven-Eleven (down 13.2%) and Toyota (down 11.9%) were the worst fallers on the index.

There is nothing particularly worrisome about these falls: with a company like Toyota giving shareholders a 60% return over the last year, something had to give.

Toyota certainly suffered from the weaker dollar, although the currency doesn't curtail its exports. There are seven Toyota plants in the US already, and last month the firm said it was studying whether to build an eighth (one of 10 in the next four years worldwide).

BBC Global 30, last 12 months

Instead, dollar income is simply worth less nowadays, even if Toyota does hope to overtake GM as the world's biggest carmaker later this year.

More remarkable was the 5.3% rise in the shares of Japanese telecom giant NTT DoCoMo.

True, there were some bullish mobile phone shipment numbers.

But the company also made it plain its future lay, not in the relentless chatting, texting or downloading of its customers, but in financial services.

Last month it launched its DCMX credit card service, allowing handsets to pay for goods and services - a business it sees as being worth more than $900m a year in three years and a gateway into as yet unspecified retail businesses.

Tech troubles

The 10 European Global 30 members fell 5.5% on average. Siemens was the worst hit, down 11.4%.

Investors are increasingly worried about mounting costs at Siemens' loss-making technology divisions and the ability of chief executive Klaus Kleinfeld to hit his 2007 profitability targets.

Vodafone has been unable to sell its stake in Verizon Wireless

Vodafone's shares were weighed down for much of the month by its inability to sell its 45% stake in Verizon Wireless of the US to Verizon itself, and Verizon's Chief Finance Officer Doreen Toben confirmed that no deal was imminent.

Verizon fell 8.2% in the month.

But Vodafone perked up after it came out with its annual results, misleadingly headlined by much of the media as the biggest loss in European corporate history.

New accounting rules meant that it had to write down the sale of its Japanese unit and the $186bn Mannesman acquisition in 2000 in a single year.

Chief Executive Arun Sarin told the BBC: "We have produced �6bn worth of free capital, we're returning �9bn to shareholders, we've increased dividends 49% to 6.07 pence per share.

"These are all signs of a very healthy company. We have 170 million customers worldwide, we've sales of over �30bn. The loss from the write-off is to do with past acquisitions."

Power problems

The month has also been marked by a series of raids on utility companies in Europe by the European Commission investigating alleged anti-competitive behaviour.

The biggest of them all, E.ON, is a Global 30 member. It is down 7.7% on the month.

E.ON Energie, the central Europe market unit of E.ON, was raided during a board meeting, and the Commission confiscated all the documents in the room.

German utility E.ON had a rough month

In contrast, BASF (down 7.5%) escaped a Commission multi-million dollar fine after an investigation exonerated it, but found ICI and three other European chemicals companies guilty of fixing certain plastics prices.

However, the month also saw BASF successful in its $5bn takeover of Engelhard, the US inventor of the catalytic converter, after putting up its offer by some 6%.

Bearing in mind the sell-off has been triggered by worries about higher interest rates, slowing growth and falling commodity prices, it's surprising the miners and oil companies did not slide effortlessly to the top of the losers' list.

They were down, but not badly: BHP Billiton, BP and CNOOC of China and Exxon all fell between 6 and 8%.

US still robust

As for the US stocks, having never flown as high as the Asian or European ones, they did not have so far to fall.

One other technical point: the index is based in sterling, so the weakening dollar means falls in US stocks have had less of an impact on the index.

Wal-Mart, after announcing its first quarter profits had risen an unexpected 6.3%, was the second-best gainer on the Index, up 4.5%.

Some of the shine was coming off the shares by the end of the month, as May sales figures looked less rosy.

GE shares slipped a modest 3.8%. Chief Executive Jeff Immelt estimated growth for the conglomerate would be two to three times faster than global GDP - that could be up to 9% to 15% a year, rather than the 8% he was previously forecasting.

Within 15 years, he believes 70% of earnings will be coming from outside the US.

So, not surprisingly, at the end of the month he was in China signing a clean energy technology agreement and in Mumbai in India talking of how GE's Indian revenues would rise to $8bn in four years.