1 • Why Learn This Skill?
The Phoenicians sailed the waters of the Mediterranean to trade cedar and purple dye for goods they did not have. They were among the most successful traders of their day. Imagine that you want to prepare a report on world trade today. You need to show a lot of information in a brief and clear way. One way you might do this is by making graphs. A graph is a diagram that shows relations between numbers. Knowing how to read and make graphs will help you see and compare large amounts of information.
2 • Bar, Circle, and Line Graphs
Different kinds of graphs show information in different ways. A bar graph, which is made up of different-sized bars, is especially useful for quick comparisons. Notice that the bars on the graph titled Selected U.S. Exports are horizontal, or go from left to right. Bar graphs can be vertical, too, with the bars going from bottom to top.
A circle graph, often called a pie chart, divides information into parts. The circle graph below shows the total amounts of the United States' exports. The parts of the graph represent the amounts of trade between the United States and certain other countries. Like other graphs, circle graphs can help you make comparisons. You can compare the parts to each other or to the whole.
A line graph shows change over time. The line graph below shows how the amount of goods exported from the United States changed between the years 1970 and 1995. Each dot shows how much trade took place in one year, and a line connects all the dots. Depending on the information, the line may go up or down or stay at the same level. Line graphs are most useful in showing a trend, or the way something changes over time.
3. Understand the Process
Compare and contrast the information in the bar, circle, and line graphs by answering the following questions. As you answer, think about the advantages and disadvantages of each kind of graph.
- Which graph or graphs would you use to find how much machinery the United States exports? Explain your choice.
- Which graph or graphs would you use to find the percent of goods the United States exports to Japan? Explain your choice.
- Which graph or graphs would you use to find how much change there was in the United States' exports between the years 1970 and 1980? Explain your choice.
- Do you think the information on the line graph can be shown on the circle graph? Explain your answer.
Using the graphs on these pages, write a paragraph summarizing information about the United States' international trade in recent years. Share your paragraph with a partner, and compare your summaries.