Although the payoff of a small niche may be less than that of a large, growing market, the competion may often also be less intense. The majority-fallacy concept states that appraisals of fast growing  segments overlook of minimize the likelihood that many competitors will be attracted. This explains why growth areas often stimulate destructive overcapacity and why a more modest product-market scope may be a preferable choice.

From Aaker, Strategic Market Management.