Since the shift began toward a majority urban population in the United States roughly a century ago, the number of people living in cities has grown continuously. Those cities have since expanded, sprawling out into surrounding areas and creating broader urban zones—the major metropolitan areas we know today. The government defines a metro area as a geographic space based around one or more core urban zones with a population of at least 50,000. Metros may exist in one county or span multiple counties, and some even cross state lines. By the government's definition, there are almost 400 metropolitan areas in the country. In total, these account for approximately 86% of the entire US population, or about 280 million people. Of that number, 50% of the urban population resides in one of the top 25 metros—areas that are only growing larger every year. For employers in and around these places, this growth and the accompanying flow of people in and out of these regions create unique vetting concerns that require special strategies to address.