Oligopolies exist for several reasons, the most common probably being economies of scale. If these are substantial, as they are in the automobile industry, for example, only very large firms can produce at minimum average cost. This makes it virtually impossible for new firms to enter the industry. A small firm could not produce at minimum cost and would soon be competed out of the business; yet to start at the required very large scale would take far more money than an unestablished firm is likely to be able to raise before proving it will be profitable.