The "driving forces" in an industry :

a. are usually triggered by changing technology or stronger learning/experience curve effects.
b. appear when an industry begins to mature but are seldom present during early stages of the industry life cycle.
c. usually are spawned by growing demand for the product, the outbreak of price-cutting, and big reductions in entry barriers.
d. are major underlying causes of changing industry and competitive conditions and have the biggest influences in reshaping the industry landscape and altering competitive conditions.
e. are usually triggered by shifting buyer needs and expectations or by the appearance of new substitute products.