Because macroeconomics is grounded in microeconomics and uses mathematical models to simplify and illustrate complex processes, learning it can be difficult. Traditional macroeconomic-principles textbooks fail to connect topics and models in a concise, cohesive, and meaningful way. So, it should not surprise when a 2008 presidential candidate says, "Economics is something that I've really never understood" (Zuckman 2008). This book overcomes these shortcomings with better topic selection and organization, by literally building a model of the macroeconomy, and utilizing a single hypothetical numerical example throughout the book to teach the principles. Keynesian economics, a school of economic thought based on the views of the British economist John Maynard Keynes (1883 to 1946), is used to construct the model of the macroeconomy because it is elegant, simplistic, intuitive, and politicians apply it when enacting stimulus bills. That said, the book is not an endorsement of Keynesian economics, nor does it suggest that mathematical modeling is the quintessential element of economic analysis. Only by building this model upon a Keynesian foundation can one truly appreciate the various perspectives in economics, the limitations of mathematical modeling, and why politicians tend to prescribe Keynesian solutions. This book allows business executives, graduate and undergraduate students, policy makers, and others to gain a fuller understanding of how the macroeconomy reacts to economic shocks and policy changes from several economic perspectives.