The Forbes 2000 is not only a comprehensive list of the world's largest, most powerful, public companies, but also unique in its way of measuring corporate size.

Our logic for using sales, profits, assets and market value in a composite ranking: A list based on a single metric provides a lopsided view of which companies are most important to the world's economy.

Selecting the largest companies strictly on sales would put Google, with $6.1 billion in revenues, way down in rank, even though it is the world's 36th largest company measured by market capitalization.

So why not rank corporations just on market value? All you have to do is go back to a year like 2000, when tiny startups, with little in the way of sales, assets, employees, or even a viable business, were suddenly valued as if they were blue chip corporations.

Forbes 2000, by: Rank | Name | Country | Industry | Sales | Profits | Assets | Market Value

An asset-ranked list has an obvious shortcoming: financial service companies would dominate.

• Forbes 2000: Full Coverage
• Slideshow: The World's 2000 Largest Companies

And a list ordered solely on corporate profits would completely miss big cyclical companies like General Motors and Ford Motor during downturns.

World's Top 10 Companies
1	Citigroup
2	General Electric
3	Bank of America
4	American Intl Group
5	HSBC Group
6	ExxonMobil
7	Royal Dutch/Shell Group
8	BP
9	JPMorgan Chase
10	UBS

For all the above reasons, we developed our composite ranking system for selecting and ordering the Forbes Global 2000. Using our methodology, Chevron ($185 billion in revenues, $14 billion in profits, $125 billion in assets and $127 billion in market) ranks 16. Chevron's ranks on the four underlying metrics range from a high of six on sales to a low of 122 on assets.

Well-known global companies like Chevron, ExxonMobil and Toyota Motor head the Forbes Global 2000, but as you drill down into the rankings, you will find companies that are not household names in America.

Today, one cannot purchase many of those companies as American Depositary Receipts (ADRs), a type of security that makes it easy for U.S. investors to hold stakes in foreign companies. That is likely to change as these companies gain in stature and recognition.

If you want to find companies that might become the international leaders of tomorrow, the Forbes Global 2000 is an excellent prospecting list.

Last year, for example, we ranked Xstrata 764 on the Forbes Global 2000; this year it climbed to 510. Based in Switzerland, this coal and metals-mining company saw double digit gains in all four metrics, highlighted by a 38% increase in market value.

• Slideshow: 20 Important IPOs
• Slideshow: Billionaires and the Global 2000
• Slideshow: Highlights of the Global 2000

Someday a company like Xstrata, which trades in Switzerland and London, might be available as an ADR.

With combined sales of $24 trillion; profits, $1.7 billion; assets $88 trillion; market value $31 trillion; and worldwide employees 68 million, the Forbes Global 2000 accounts for a significant chunk of the global economy. This year's rankings, which span 55 countries, show the gains of emerging economic dynamos such as China and India.

We now include 36 companies based in Hong Kong/China, a gain of eight over the previous list; 28 in mainland China, up three; and 33 in India, up three.

Top 50 In Sales
With a 24% jump in 2005 revenues, ExxonMobil moved past last year's world revenues champ, Wal-Mart Stores. Of the sales leaders, 20 hail from the U.S.

Top 50 In Profits
Higher oil and gas prices helped energy companies grab six of the top ten spots here. ExxonMobil's record profits last year: $36 billion.

Top 50 In Assets
Financial service companies rule this list. Barclays of the U.K. unseats perennial asset leader Citigroup to claim the top spot in assets.

Top 50 In Market Value
Despite an 11% decline in market value from last year, ExxonMobil, capitalized at $363 billion, remains the world's most valuable company.

From Top to Bottom

Of the Forbes Global 2000 companies, the banking sector is the biggest group by number, with 310 companies, and by workforce, with 6 million people worldwide. For the second consecutive year the oil and gas group ranks first in aggregate revenues.

• Slideshow: Global 2000 Face-off
• Slideshow: India's Hottest Jobs

Do you want to discuss stock tips? Do you know a hot one? Join the Stock Market Discussion Group.