When the first edition of this textbook was published in 1996, the World Bank defined “low-income country” as one with per capita income of less than \($501.\) In 2003, when the third edition of Global Marketing appeared, “low income” was defined as \($785\) or less in per capita income. As shown in Table 2-4, \($1,005\) is the current “low-income” threshold. The other stages of development have been revised in a similar manner. How do you explain the trend in the definition of income categories during the past 20 years?