Barriers to Entry : a theoretical treatment

I was originally induced to think about barriers to entry by some re search done for Charles River Associates, Inc., Boston, on behalf of their client IBM Corporation, Armonk, N.Y. After the end of this re search project I continued to work on entry barriers and related is sues of market structure. The results of this effort are reported here. What I present is not a book in the traditional sense of the word. Due to other research and administrative obligations I could not, without substantial delay, present a more finished product. The rapid progress in the field of industrial organisation theory made me fear that my results could become obsolete if I further waited with their publica tion. I hope that the early presentation of a progress report rather than a much later publication of a finished product is not only in my interest but also in the interest of economics.