The final step in building customer profiles is to identify external factors that influence buyers. These influences include the government, social change, economic shifts technology, and other environmental factors that alter buyers' needs and wants.

Typically these factors are not controlled by the buyer or the firms that market the product Substantial changes in these influences can have a major impact on customers. Therefore it is important to identify the relevant external influences on a product-market and estimate their future impact. During the past decade various changes in market opportunities occurred as a result of uncontrollable environmental factors. Illustration includes the shifts in age-group composition, changes in tax laws affecting investments and variations in interest rates.

Consider, for example, the population trends for the states in the United States from 1990 to 2000. Some states (Exhibit 3-4) have high growth rates while others have declined in size. .