MicroeconomicGRAPHSINECONOMICS文件材料.ppt

1;Economists measure variables that describe what, how, and for whom goods and services are produced. These variables are quantities produced and prices. Figure A1.2 shows two examples of economic graphs.;Figure A1.2(a) is a graph about iTunes song downloads in January 2010. Point A tells us what the quantity and price were. You can “read” this graph as telling you that in January 2010: 8.3 million songs a day were downloaded at a price of 99￠ per song.; ;Scatter Diagrams A scatter diagram plots the plots the value of one variable against the value of another variable for a number of different values of each variable. A scatter diagram reveals whether a relationship exists between the two variables. Figure A1.3 (on the next slide) shows some data on box office tickets sold and the number of DVDs sold for nine of the most popular movies in 2009. The table gives the data and the graph describes the relationship between box office tickets sold and DVD sales.;Figure A1.4(b) is a scatter diagram of inflation and unemployment in the United States during the 2000s. The points for 2000 to 2008 show no relationship between the two variables. But the high unemployment rate of 2009 brought a low inflation rate that year.;Graphs are used in economic models to show the relationship between variables. The patterns to look for in graphs are the four cases in which Variables move in the same direction. Variables move in opposite directions. Variables have a maximum or a minimum. Variables are unrelated.;Variables That Move in the Same Direction A relationship between two variables that move in the same direction is called a positive relationship or a direct relationship. A line that slopes upward shows a positive relationship. A relationship shown by a straight line is called a linear relationship. The three graphs on the next slide show positive relationships.;Graphs used in Economic Models;Variables That Move in Opposite Directions A relationship between two variables that