Every marketer must decide how much time and money to invest in each of the four areas of the marketing mix. The decision must be objective; no one can afford to invest money in a marketing strategy that does not provide a good return on money invested. Personal selling is often the major promotional method used—whether measured by people employed, by total expenditures, or by expenses as a percentage of sales. As noted in Chapter 1, there are more than 21 million field and retail salespeople in the United States. This represents about 11 percent of all of the people who are employed full time. Approximately 6 million of these salespeople have field responsibility. Full-time salespeople in the United States cost their companies more than a trillion dollars every year and represent by far the largest marketing expenditure. This is more than four times what is spent on advertising.9

Firms make large investments in personal selling in response to several major trends: Products and services are becoming increasingly sophisticated and complex; competition has greatly increased in most product areas; and demand for quality, value, and service by customers has risen sharply. In response to these trends, personal selling has evolved to a new level of professionalism. Since the beginning of the information age, personal selling has evolved through three distinct developmental periods: the consultative-selling era, the strategic-selling era, and the partnering era.