What does the consumption function illustrate in economics?

The consumption function is a key concept in economics that illustrates the relationship between disposable income and consumption spending by households. It shows how much households plan to spend on goods and services at different levels of disposable income. Essentially, it highlights the idea that as disposable income increases, consumption typically rises as well, although the increase happens at a decreasing rate.

This relationship is fundamental for understanding consumer behavior and its impact on the overall economy. It is also significant for policymakers when assessing how changes in income tax or other economic policies might influence consumer spending. In contrast, the other options present different economic concepts that do not directly relate to the specific relationship defined by the consumption function, emphasizing total income, taxation policies, or government spending, rather than the direct link between disposable income and consumption levels.