In business theory, a disruptive innovation is an innovation that creates a new market and value network and eventually disrupts an existing market and value network, displacing established market-leading firms, products, and alliances. The term was defined and first analyzed by the American scholar Clayton M. Christensen and his collaborators beginning in 1995,and has been called the most influential business idea of the early 21st century. Not all innovations are disruptive, even if they are revolutionary. For example, the first automobiles in the late 19th century were not a disruptive innovation, because early automobiles were expensive luxury items that did not disrupt the market for horse-drawn vehicles. The market for transportation essentially remained intact until the debut of the lower-priced Ford Model T in 1908.  The mass-produced automobile was a disruptive innovation, because it changed the transportation market, whereas the first thirty years of automobiles did not. Disruptive innovations tend to be produced by outsiders and entrepreneurs in startups, rather than existing market-leading companies