Authorities provide differing definitions of the middle-market or mid-market companies. While some authorities look to revenue generated by companies to define the middle market, other sources regard either asset size or number of employees as a better metric for comparing company sizes. Definitions of the middle market are generally derived by dividing the United States economy into three categories: small business, middle-market, and big business. According to figures collected by the U.S. Census Bureau, the total revenue of all U.S. businesses in 2012 was roughly $32.6 trillion. The largest of these companies, which are big businesses with revenue of over $3 billion, make up roughly one-third of that total, and businesses with a revenue of under $100 million made up about another third of the total revenue. The middle market can thus be defined as the companies larger than small businesses but smaller than big businesses that account for the middle third of the U.S. economy's revenue. Other authorities define middle-market firms differently. The National Center for the Middle Market at the Ohio State University Fisher College of Business as well as Dun & Bradstreet’s proprietary database of commercially-active U.S. firms define middle market businesses as those companies with revenues between $10 million and $1 billion per year. The definition is defined in reference to small businesses, which earn less than $10 million in annual revenue, and big business, which earn at least $1 billion in revenues and are generally the smallest eligible for a credit rating by one of the "major" credit-rating agencies. Investopedia considers middle market firms to be those with sizable annual revenues, ranging from $50 million to $1 billion, which straddle the market between smaller companies and billion-dollar giants. In the United States The 200,000 plus US-based mid-market companies are essential to America's economic success. They account for $10 trillion annually of the $30 trillion U.S. private sector gross receipts and 30 million jobs. If the U.S. middle market were a country, its GDP would rank it as the fourth-largest economy in the world. In Europe Mid-market companies—companies that are too big to be considered SMEs, but smaller than big, exchange listed businesses—play a key role in the UK and in the other top European economies. According to an in depth report by ESSEC Business School and GE Capital, across the UK, Germany, France and Italy (the EU-4), the mid-market represents a relatively small number of