BP drops out of BBC index of world's biggest firms

When the markets are on a roller coaster, companies tend to get hurled off at the sharp bends, which is why the constituents of the BBC Global 30 index (the thirty biggest companies in the world) have had such a radical shake up, with nine changes, more than ever before.

With its chief executive under fire during his appearence before US lawmakers this week, it can't be that much of a surprise that BP has lost its position, with its share price down by more than a third.

Shell has taken its place, which has a certain irony since BP overtook Shell as Europe's largest oil company just before the Gulf oil spill.

BP was cutting costs faster and more aggressively and reaping the rewards.

All that is rather academic now, and Shell's investors are the happier bunch: for starters, they have a dividend, and they don't have an oil spill.

However, it is worth remembering that Shell is the second largest oil producer in the Gulf of Mexico, and although it and the other "Big Oil" brethren swear blind that the Gulf spill would never have happened on one of their rigs, offshore drilling could face serious obstacles.

While the oil companies have been facing up to lower oil prices as the global economy makes its painful recovery, the miners have been ratcheting up their prices, thanks to China's economy resuming its upward trajectory.

The king of the commodities is gold, with the yellow metal regularly testing new highs. So Barrick Gold of Canada, the world's largest gold miner, has stepped confidently into the Global 30.

Barrick's profits doubled in the first quarter of this year, although the company claims it is not just the gold price that has pushed up its shares, but increased margins, reduced costs, and a pile of new projects ready to go.

The market has also been rumouring it is ready for a big merger - possibly with Australia's Lihir Gold.

Rio Tinto also enters the index while BHP Billiton has moved out. There's no dramatic change here.

The two are evenly balanced; both face the 40% supertax being wielded by the Australian government, and both have massive international commodity operations, although Rio is bigger in iron ore and aluminium while BHP offers oil and gas exposure which Rio doesn't have.

All the same, Rio's shares have outperformed BHP's since it abandoned the sale of a $US19.5bn (£13.2bn) stake to its Chinese customer Chinalco.

It instead opted for a $15.2bn rights issue and asset sales worth more than $10bn, which put its balance sheet on a more stable footing.

But its expansion plans are less impressive than BHP's. Rio expects to spend US$5-6bn compared with BHP's US$11.5bn. So BHP's absence from the index may be short lived.

The other big arrival in the Global 30 is Berkshire Hathaway in the financial sector.

Warren Buffet's investment vehicle is an anomaly: while it is one of the 20 biggest companies on the US market, the shares have been notoriously illiquid, not even meriting a place on the S&P 500.

But its biggest acquisition ever, of the US railway company Burlington Northern, forced it to split its B shares into 50 - Burlington shareholders wouldn't accept anything bigger.

The surge in liquidity has given it an entree into global indices, and its value as an economic indicator, with its spread of business investments in everything from insurance to retail and manufacturing, is obvious: so optimists on the economy can take comfort from the fact that in the first quarter it bounced back from last year's loss to report US$3.6 billion in net income.

Diversification is a good bet in wild times.

The Australian Wesfarmers group has also been gathering together a broad range of businesses - retail, hardware, resources, insurance and chemicals.

That's protected the share price but it's primarily in the Global 30 thanks to the turnaround of its Coles retail operation, which it bought back in 2007 in Australia's biggest take-over yet.

Now it's thought to be looking for more acquisitions.

The world slowdown doesn't really seem to apply to electronics, where the pace seems as feverish as ever.

Samsung is back in the Global 30 thanks to a rebound in chip sales as customers started to buy PCs again.

Nokia is out as investors grow ever more impatient with its failure to find a credible competitor to Apple's iPhone.

Samsung came up with the Galaxy S, and it is staking much of its fortunes on tripling its 5% smartphone market share this year.

The competition is cut throat as ever and one gets the impression that no one gets to stay as top dog for long - something that may well apply to global markets as a whole next year as well as this.