Actions by the Federal Government that decrease the progressivity of the tax system:

a. decrease the amount of government spending
b. increase the effects of automatic stabilizers
c. decrease the effects of automatic stabilizers
d. increase the amount of taxation

To determine which actions by the Federal Government decrease the progressivity of the tax system, we need to understand the concept of progressivity and its relationship to different fiscal policies.

Progressivity refers to a tax system where the tax burden increases as income increases. In other words, individuals with higher incomes pay a higher proportion of their income in taxes than those with lower incomes. Conversely, a decrease in progressivity means that the tax burden becomes relatively less burdensome for higher-income individuals.

Now, let's assess each option in relation to its impact on the progressivity of the tax system:

a. Decrease the amount of government spending: This action alone does not directly impact the progressivity of the tax system. Government spending affects the overall fiscal health and the size of the public debt; it does not directly alter the progressivity of taxes.

b. Increase the effects of automatic stabilizers: Automatic stabilizers are policies that automatically stimulate or contract the economy during times of economic expansions or contractions. Since this action does not explicitly address taxes, it is unrelated to the progressivity of the tax system.

c. Decrease the effects of automatic stabilizers: Similarly, decreasing the effects of automatic stabilizers is unrelated to the progressivity of the tax system. It may affect the overall economy but does not influence the distribution of tax burden across income levels.

d. Increase the amount of taxation: This action could potentially decrease the progressivity of the tax system. By increasing the amount of taxation, the tax burden would likely increase for everyone, affecting both lower and higher-income individuals. However, unless certain tax brackets or rates were changed, the progressivity might not necessarily change.

In conclusion, the action that is most likely to decrease the progressivity of the tax system is option d - increasing the amount of taxation. Nonetheless, changes to specific tax brackets or rates would have a more direct impact on progressivity. It is vital to note that other factors, such as tax exemptions, deductions, and credits, can also influence the progressivity of the tax system.