The important thing to keep in mind when being sued by charge card company or junk debt buyers is that if they don't have proof that would otherwise prove how the debt is yours, they do not have a very case. For junk debt buyers, you're in luck since these agencies would not have the essential documents that would prove you have the debt, being a signed contract between you and the original creditor, because these documents aren't released with the original creditor. 3. The role of securities investment Historically, the concept of income has first appeared in economics. Adam Smith, in the wealth of nations, defined income as "the amount of consumption that is not eroded by capital", and saw it as an increase in wealth. Later, most economists inherited and developed this view. 1890, ai (Alfred Marshall Maarshell) in its "the principles of economics," the Adam Smith's "wealth increase" enterprise, introduced the concept of earnings, is proposed to distinguish the entity capital and value-added benefits of economic benefits.