Pacific Oceans, as well as on the Gulf of Mexico. Rivers flow from far within the continent and the Great Lakes (the five large inland lakes along the Canadian border) provide additional shipping access. These extensive waterways have helped shape the country's economic growth over the years and helped bind America's fifty individual states together in a single economic unit. The number of workers and, more importantly, their productivity help determine the health of the U.S. economy. Consumer spending in the U.S. rose to about 62% of GDP in 1960, where it stayed until about 1981, and has since risen to 71% in 2013. Throughout its history, the United States has experienced steady growth in the labor force, a phenomenon that is both cause and effect of almost constant economic expansion. Until shortly after World War I, most workers were immigrants from Europe, their immediate descendants, or African Americans who were mostly slaves taken from Africa, or their descendants. Demographic shift Beginning in the late 20th century, many Latin Americans immigrated, followed by large numbers of Asians after the removal of nation-origin based immigration quotas. The promise of high wages brings many highly skilled workers from around the world to the United States, as well as millions of illegal immigrants seeking work in the informal economy. More than 13 million people officially entered the United States during the 1990s alone. Labor mobility has also been important to the capacity of the American economy to adapt to changing conditions. When immigrants flooded labor markets on the East Coast, many workers moved inland, often to farmland waiting to be tilled. Similarly, economic opportunities in industrial, northern cities attracted black Americans from southern farms in the first half of the 20th century, in what was known as the Great Migration. In the United States, the corporation has emerged as an association of owners, known as stockholders, who form a business enterprise governed by a complex set of rules and customs. Brought on by the process of mass production, corporations, such as General Electric, have been instrumental in shaping the United States. Through the stock market, American banks and investors have grown their economy by investing and withdrawing capital from profitable corporations. Today in the era of globalization, American investors and corporations have influence all over the world. The American government is also included among the major investors in the American economy. Government investments