Each of the new observations in the table has been labeled with a prime: A′, B′, etc. If no games had been canceled during the 1998–1999 basketball season, Shaquille O’Neal would have earned $17,220,000 (point A). The slope is thus, [latex]Slope = \frac{vertical\ change}{horizontal\ change} = \frac{- \$ 6,720,000}{32 : games} = - \$ 210,000/game[/latex]. Throughout this course we will refer to the horizontal line at the base of the graph as the x-axis. Figure 35.4 Computing the Slope of a Curve. The second combination, B, tells us that if 10 passengers ride the bus, the club receives $300 in revenue from the trip—$100 from the $10-per-passenger charge plus the $200 from student government. We have drawn vertical lines from each of the values on the horizontal axis and horizontal lines from each of the values on the vertical axis. Panel (b) shows the computation of the slope of the new curve between points B′ and C′. The change in the horizontal axis is from zero games canceled at A to 32 games canceled at B. Recall that, when two variables are related, the dependent variable is the one that changes in response to changes in the independent variable. 58 units, 86. © Dec 2, 2022 OpenStax. As an example of a graph of a negative relationship, let us look at the impact of the cancellation of games by the National Basketball Association during the 1998–1999 labor dispute on the earnings of one player: Shaquille O’Neal. Recall that, when two variables are related, the dependent variable is the one that changes in response to changes in the independent variable. The two variables shown in the table are the number of passengers taking the bus on a particular day and the club’s revenue from that trip. Arrow “B” indicates this. Reading to the left from point B, we see that it shows $300 in club revenue. We repeat this process to obtain points C, D, and E. Check to be sure that you see that each point corresponds to the values of the two variables given in the corresponding row of the table. Now suppose you are given the following information about the relationship between price per gallon and the number of gallons per week gas stations in the community are willing to sell. The slope of a curve is the ratio of the vertical change to the horizontal change between two points on the curve. Notice that we can compute the slope of R1 between any two points on the curve and get the same value; the slope is constant. The curve’s downward slope tells us there is a negative relationship between price and the quantity of gasoline people are willing and able to buy. Suppose a college campus has a ski club that organizes day-long bus trips to a ski area about 100 miles from the campus. Understanding and creating graphs are critical skills in macroeconomics. By the end of this section, you will be able to: John Maynard Keynes (1883–1946), one of the greatest economists of the twentieth century, pointed out that economics is not just a subject area but also a way of thinking. The final step is to draw the curve that shows the relationship between the number of passengers who ride the bus and the club’s revenues from the trip. Notice also that R1 intersects the vertical axis at $200 (point A). The aggregate demand-aggregate supply (AD-AS) model Panel (a) of Figure 35.8 “Rotating a Curve” shows what happens to the original revenue curve, R1, when the price per ticket is raised. Let us change one. Develop an understanding of economic theories, history, and practice. What is the best way to learn economics diagrams/graphs? A curve whose slope is positive is upward sloping. It is customary to place the independent variable on the horizontal axis and the dependent variable on the vertical axis. Relationships or connections - graphs in economics illustrate the relationship between two variables, typically, using a line graph. Creative Commons Attribution License Zoom out for a moment: what is the overall economic story being portrayed in the graph? The new values are shown as combinations A″ through E″ on the new curve, R3, in Panel (b). Economics How to Read GDP Reports The two variables shown in the table are the number of passengers taking the bus on a particular day and the club’s revenue from that trip. The shifts in Figure 21.6 “Shifting a Curve: An Increase in Revenues” and Figure 21.7 “Shifting a Curve: A Reduction in Revenues” left the slopes of the revenue curves unchanged. The greater the slope of a positively sloped curve, the steeper it will be. We’d love your input. As we travel down and to the right along the curve, the number of games canceled rises and O’Neal’s salary falls. We travel up by $300 and mark point B. We have extended the vertical axis to $800 to allow some changes we will consider below. It pictures the economy as consisting of two groups—households and firms—that interact in two markets: the goods and services market in which firms sell and households buy and the labor market in which households sell labor to business firms or other employees. 1.3 How Economists Use Theories and Models to Understand Economic ... The table relates various combinations of the number of passengers and club revenues. Unit 3: National Income and Price Determination. It is important that you understand how to use them. Draw a line through the points you have plotted. Applying the equation, we have: [latex]Slope = \frac{vertical \: change}{horizontal \: change} = \frac{ \$ 200}{20 \: passengers} = \$ 10/passenger[/latex]. The fact that it is positive suggests a positive relationship between revenue per trip and the number of passengers riding the bus. Rather, they use the graph of the theory to help them figure out the answer. Why Are Graphs Used in Economics? The point where two lines on a graph cross is called an intersection point. The new curve is shown in dark purple in Panel (b). The axes should be carefully labeled to reflect what is being measured on each axis. At B, it is $10,500,000. The change in the horizontal axis when we go from B to D thus equals 20 passengers. Consider, for example, points A and E. The vertical change between these points is $400 (we go from revenues of $200 at A to revenues of $600 at E). The slope between B and C and between A and C is the same. The point at which a curve intersects an axis is called the intercept of the curve. What information is being described on the x-axis and the y-axis? The club’s only revenue now comes from the $10 it charges to each passenger. Thank you for watching my econ videos. NOTE: Around the two-minute mark, the narrator inadvertently says “indirect,” rather than “inverse.” This is corrected later in the video. That is because the slope in all these cases equals the price per ticket, and the ticket price remains unchanged. We begin our graph in Panel (a) of Figure 35.2 “Plotting a Graph” by drawing two axes to form a right angle. Passengers generate revenue, so we can consider the number of passengers as the independent variable and the club’s revenue as the dependent variable. Once again we have a shift in a curve, this time from R1 to R3. In this section, we will see how to compute the slope of a curve. If so, in which direction does the relationship flow? We have again changed one of the variables we were holding unchanged, so we get another shift in our revenue curve. In the table, each combination is assigned a letter (A, B, etc. How To Read Graphs - Public Goods - Hayden Economics Notes for Economics www.saseassociates.comA quick general review of graph types use in Economics:These include:a straight upward sloping line with a constant. Reading to the left from point B, we see that it shows $300 in club revenue. We start at 10 passengers on the horizontal axis and follow the gridline up. We can start with 0 on the. The fact that the slope of our curve equals $10/passenger tells us something else about the curve—$10/passenger is a positive, not a negative, value. Mathematically, the x-intercept is the value of x when y = 0. They relate the values of the variables on the two axes to each other. Connect Master: Principles of Economics, the first video-based approach for principles of economics, is the ideal way to engage today's digital native learner. Label the x axis "Real GDP" and the y axis "Price level". Sometimes we use symbols in place of words. In Equation 35.1 there are three variables: the slope, the vertical change, and the horizontal change. As noted above, the b term is the y-intercept. To check your understanding of these steps, we recommend that you try plotting the points and drawing R1 for yourself in Panel (a). The slope tells us how steep a line on a graph is as we move from one point on the line to another point on the line. 8 Key Macroeconomics Graphs - AP/IB/College - ReviewEcon.com The slope of this curve tells us the amount by which revenues rise with an increase in the number of passengers. At 58 units we're at 86. Because the curve is linear, the slope is the same between any two points, for example, between E and F and between D and F. Principles of Economics by University of Minnesota is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted. Each axis will represent a variable. Here is the first graph. Here the x axis is Q, quantity, and the y axis is P, price. A downward-sloping curve suggests a negative relationship between two variables. Keynes (Figure 1.6) famously wrote in the introduction to a fellow economist’s book: “[Economics] is a method rather than a doctrine, an apparatus of the mind, a technique of thinking, which helps its possessor to draw correct conclusions.” In other words, economics teaches you how to think, not what to think. This method is quickly growing in popularity among students and faculty across all course formats: traditional, online, flipped, and hybrid. Figure 35.5 Canceling Games and Reducing Shaquille O’Neal’s Earnings. Notice that this time the slope is negative, hence the downward-sloping curve. https://openstax.org/books/principles-economics-3e/pages/1-introduction, https://openstax.org/books/principles-economics-3e/pages/1-3-how-economists-use-theories-and-models-to-understand-economic-issues, Creative Commons Attribution 4.0 International License, Explain the importance of economic theories and models, Describe goods and services markets and labor markets. What is the slope between D and E? We explain both micro and macroeconomics in terms of theories and models. A graph is a pictorial representation of the relationship between two or more variables. Plot the Points The production possibilities frontier is constructed by plotting all of the possible combinations of output that an economy can produce. Graphs of MC, AVC and ATC (video) If no games had been canceled during the 1998–1999 basketball season, Shaquille O’Neal would have earned $17,220,000 (point A). The rule that the independent variable goes on the horizontal axis and the dependent variable goes on the vertical usually holds, but not always. Equation 21.1 is the first equation in this text. An upward-sloping curve suggests a positive relationship between two variables. Now suppose that, instead of increasing its payment, the student government eliminates its payments to the ski club for bus trips. Figure 2. A curve with a negative slope is always downward sloping. Does your graph suggest a positive or a negative relationship? This point shows that zero passengers result in club revenues of $200. In this graph, we have inserted a break in the vertical axis near the origin. The procedure for showing the relationship between two variables, like the ones in Figure 35.1 “Ski Club Revenues”, on a graph is illustrated in Figure 35.2 “Plotting a Graph”. With 10 passengers, for example, the club’s revenue was $300 at point B on R1. The slopes of curves tell an important story: they show the rate at which one variable changes with respect to another. A rotation in the curve implies that one point remains fixed while the slope of the curve changes. How do we interpret supply and demand graphs The club’s only revenue now comes from the $10 it charges to each passenger. A good theory is simple enough to understand, while complex enough to capture the key features of the object or situation you are studying. The graph we drew in Figure 35.2 “Plotting a Graph” shows the relationship between club revenues from a particular trip and the number of passengers on that trip, assuming that all other variables that might affect club revenues are unchanged. The greater the slope of a positively sloped curve, the steeper it will be. You may have heard this called “the rise over the run.” In equation form, we can write the definition of the slope as. Learn more about how Pressbooks supports open publishing practices. The change in the horizontal axis when we go from B to D thus equals 20 passengers. The vertical intercept in this case shows the revenue the club would receive on a day it offered the trip and no one rode the bus. Between D and F? In this example, the equation is written in words. We begin with the first row, A, corresponding to zero passengers and club revenue of $200, the payment from student government. However, there are three main types of economics graphs, and they include line, bar, and pie graphs. When they see an economic issue or problem, they go through the theories they know to see if they can find one that fits. Interpreting the aggregate demand/aggregate supply model That means there was a linear relationship between games canceled and his 1998–1999 basketball earnings. Plot these points in the grid provided and label each point with the letter associated with the combination. This curve, by the way, is a demand curve (the next one is a supply curve). Point A does not change; the club’s revenue with zero passengers is unchanged. Does a change in x necessarily cause a change in y? In this course, we will mostly use graphs.) Did you have an idea for improving this content? They relate the values of the variables on the two axes to each other. The slope is thus, [latex]Slope = \frac{vertical \: change}{horizontal \: change} = \frac{- \$ 6,720,000}{32 \: games} = - \$ 210,000/game[/latex]. As we travel up and to the right along R1, we travel in the direction of increasing values for both variables. . The point at which the axes intersect is called the origin of the graph. In April 2023, prices had increased by 4.9 percent compared to April 2022 according to the 12-month percentage change in the consumer price index - the monthly inflation rate for goods and services in the United States. Canceling games reduced his earnings, so the number of games canceled is the independent variable and goes on the horizontal axis. Figure 35.7 Shifting a Curve: A Reduction in Revenues. Principles of Economics/Graphs - Wikibooks When starting to study economics, immerse yourself in existing academic literature on the topic. Is the relationship linear? Companies often build models of their new products, which are more rough and unfinished than the final product, but can still demonstrate how the new product will work. The slope of O’Neal’s salary curve is also constant. (slope = vertical change/horizontal change = −0.20/100). We begin with the first row, A, corresponding to zero passengers and club revenue of $200, the payment from student government. Similarly, the y-intercept is the value of y when x = 0. Much of the analysis in economics deals with relationships between variables. If the number of passengers increases to 30, the club will be at point D′ on the curve. x affects y and y affects x). The point at the top right indicates Q* quantity of a good each being sold at price P*; the horizontal and vertical lines are there for facilitation/marker purposes. A curve whose slope is constant suggests a linear relationship between two variables. Creating and Interpreting Graphs | Microeconomics The slope of a curve equals the ratio of the change in the value of the variable on the vertical axis to the change in the value of the variable on the horizontal axis, measured between two points on the curve. The club’s revenues from any single day thus equal $200 plus $10 times the number of passengers. Take the market for any good – let’s say running sneakers. The club’s only revenue from a trip now comes from its $10/passenger charge. It’s important to feel comfortable with the way graphs work before using them to understand new concepts. The Ultimate AP Macroeconomics Cheat Sheet (Graphs Included!) The data represents U.S. city averages. The PCE price index increased 0.4 percent. In Panel (b) we see that the original curve relating club revenue to the number of passengers has shifted down. Putting these same numbers on a graph, listing them from highest to lowest, would reveal population patterns much more readily. [latex]Slope = \frac{vertical\ change}{horizontal\ change}[/latex]. Figure 21.5 Canceling Games and Reducing Shaquille O’Neal’s Earnings. The basic idea though, is always the same: the term represented on the left side of the equals sign equals the term on the right side. Plot these points in the grid provided and label each point with the letter associated with the combination.