EU: World's biggest market.

BYLINE: Jonathan Bensky

European Union offers great opportunities for U.S. companies, but there are also plenty of challenges

The European Union is the largest economy in the world. It has a gross domestic product of about 13 trillion euros ($18 trillion), compared with about $11.5 trillion for the United States. Growth in the euro zone -- the 13 member nations that use the euro as their currency -- grew 2.7 percent last year, while other EU countries grew even faster. Unemployment, although higher than in the U.S., is at its lowest level in at least 15 years. Last year, labor productivity matched that of the U.S., again for the first time in many years.

The EU is also a huge market, with a population of nearly 500 million. The addition of Bulgaria and Romania on Jan. 1 increased its membership to 27 nations.

The U.S. and EU have the largest bilateral trade and investment relationship in world history. Together they account for more than half of the global economy, while bilateral trade accounts for 7 percent of the world total. U.S. and EU companies have invested an estimated $2 trillion in each other's economies, employing directly and indirectly as many as 14 million workers. Nearly every U.S. state is involved with exporting to, importing from or …