The most important changes in the American social contract since 1776 have been driven by technological innovations that have reshaped society in the United States and other countries. Three industrial revolutions have transformed American society, by altering the livelihood of most Americans and shifting the work force from one economic sector to another.
The three successive industrial revolutions of the past two centuries presented challenges that Americans attempted to solve by methods that reflected liberal and republican values in a society more diverse than the homogeneous nation-states of western and northern Europe. The successive incarnations of American society can be described as three informal republics of the United States.
The "First Republic" of the United States was an agrarian society. Its social contract is known by the shorthand phrase, "Jeffersonian Democracy." The "Second Republic," created by the first industrial revolution of steam power and rail, had an early industrial economy. Its social contract took shape in the Progressive Era. The “Third Republic," created by the second industrial revolution of electricity and the internal combustion engine in automobiles and aircraft, was characterized by employment in routine service sector industries. Its social contract was provided by the New Deal, the GI Bill, and by landmark Great Society and civil rights laws.The economy of the "Fourth Republic," which is being created by the third industrial revolution of automation and globalization, is one of increasing employment in personal-service jobs. A fourth social contract, building on the foundations of the previous three yet suitable for the 21st century, has yet to be constructed for the Fourth Republic in which we already live.