For all its benefits, the newfound power of real estate has also left the country open and vulnerable to a massive housing crash. Residential housing now makes up 16 percent, or $1.9 trillion, of the gross domestic product and is the US economy's largest single sector, slightly bigger than the industries and services that supply health care, according to Economy.com. Given Real Estate’s influence over economic growth this is quite significant. What will happen if it all comes crashing back to earth. Here are some facts about the US Economic empire that may or may not put your mind at ease. About 50% of the world's 500 billionaires and a 30% of the 27 million millionaires call the United States home. Almost half of the largest companies and banks in the world are US and one third are from the European Union. Five of the top ten banks are US, six of the top ten pharmaceutical/biotech companies, four of the top ten telecommunications companies, seven of the top information technology companies, four of the top gas and oil companies, nine out of the top ten software companies, four of the top ten insurance companies and nine of the top ten general retail companies. The US dominates global weapons sales, exporting more than the next 14 countries combined - The US economy depends on a massive flow of funds from overseas investors to sustain its external deficit. In other words, as empire grows, the 'republic' goes into deeper crises, stripped of its competitive enterprises and unable to limit its consumer imports. Recently Oil prices have been under pressure as troubles in the US housing finance sector have heightened fears in world stock markets about the health of the economy in the United States, the world's biggest oil consumer. Investors are concerned that a growing number of mortgage defaults by higher-risk borrowers in the United States could hit the broader financial sector and have a negative effect on consumer confidence. The big question mark is about the US economy and worries over the housing industry because that will have a big impact on consumer demand, which may affect oil consumption. The green currency lost 1.5 percent compared to the euro, which at the end of the week was trading at 1.3312 dollars. The financial markets are nervous about the ever growing problems on the US market of home loans and housing, which was supported by the ex governor of the American Central Bank, Alan Greenspan, warning on Thursday that problems in the sectors of home loans could extend to other sectors. The question remains does the upside outweigh the downside and who are we going to take down with us if things go badly? The USA is not the only economy in the world right now with record consumer debt levels and an inflated real-estate sector.