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The following message was submitted through the AP/IB Econ Help Desk:

Jason,

An AP Macro Question: Comes from the recently published AP Practice Exam

An increase in which of the following is most likely to promote economic growth?

A. Consumption Spending
B. Investment Tax Credits
C The natural rate of unemployment
D The trade deficit
E Real Interest Rates.

The answer is B, and I understand the economic principles of why that would promote economic growth, but what I can’t answer for my students is why A, Consumption Spending wouldn’t work. I know that consumption spending makes up part of the demand in aggregate demand, but I can’t help but think that an increase in it, would promote economic growth.

Thanks, “Econ Teacher”

For what it’s worth, here is my reply:

Hello “Econ Teacher”,

That’s a good question. I would explain to my students that in the short-run, an increase in AD alone will lead to some growth, but would be accompanied by inflation, since AS does not shift out when consumption increases. However, an investment tax credit will result in REAL long-run economic growth (by real I mean nominal GDP will increase while the price level remains stable), since it encourages investment. Investment is a determinant of AD, just like consumption, so AD will shift out, but it is also a determinant of AS, since firms are investing in capital. Increase the quantity or the quality of capital, and labor becomes more productive. Greater productivity shifts out AS, leading to growth AND stable prices.

Economic growth is defined, in terms of the AD/AS model, as an outward shift of both AD and AS. Increases in consumption will increase AD, but this will lead to inflation, and in the long run, workers will demand higher wages, increasing the costs of production and shifting AS leftward, returning the economy to the full employment level of output at an even higher price level, i.e. no economic growth occurs (see graph to the right). Investment, however, encouraged through a tax credit, will have positive demand and supply side effects, resulting in real economic growth and stable prices (see graph below)

Hope that helps!

Jason Welker

About the author: Jason Welker is a teacher at Zurich International School in Switzerland, where he teaches Advanced Placement and International Baccalaureate Economics. Jason was an international school student in Malaysia before studying economics at Seattle University then earning his Masters in Education. He calls Seattle and Northern Idaho home. In addition to maintaining an economics wiki and this blog for economics student and educators, Jason also gives presentations on using Web 2.0 tools in education at workshops and conferences around the world. His economics wiki won the 2007 "Best Educational Wiki" award from the "EduBlog Awards".

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