Suppose the United States were to convert its tax system from an income tax to a national sales tax on sales of goods and services. Certain necessities, like food, would be exempted from taxation, and...

Suppose the United States were to convert its tax system from an income tax to a national sales tax on sales of goods and services. Certain necessities, like food, would be exempted from taxation, and low-income households would be granted tax refunds. Would such a tax system eliminate incentives to shift activities?

 (a) from one period to the next,

 (b) from one type to another, and

(c) from one pocket to another?