Which of the following are true of the expenditure multiplier concept? Select the correct answer below: It is the concept that increasing national income affects the equilibrium level of GDP on par with the amount of increased income. It is the idea that decreasing national income affects the equilibrium level of GDP by the same amount of that decrease in income. It is the concept that an increase in spending causes a more than proportionate change in GDP. The expenditure multiplier is the idea that a given change in spending leads to an equal change in the equilibrium level of GDP.