Charts to read and discuss

Questions to discuss

1. In one sentence of your own, what does this chart show?
2. Find the biggest change or difference in the chart. What might explain it?
3. Who collected these numbers, and how recent are they? What else would you want to know before drawing a conclusion?

How to read this chart

Each point is the number of people alive in the world in the middle of that year, estimated by the United Nations. The axis starts at zero, so the height of the line shows the true size. Look at how steep the line is to see how fast the population grew.

Questions to discuss

1. Judging from the chart, about how many years did it take the world to add its most recent billion people?
2. Is the line getting steeper or flatter in recent years? What does that tell you about the growth rate?
3. These numbers are estimates that the UN revises. Why is it hard to count every person on Earth?

How to read this chart

Each bar is the number of murders in a city in one year for every 100,000 people its police department serves. The dashed line is the U.S. rate. Murders are rare, so in a smaller city a handful more or fewer in one year can move its rate and its rank a lot.

Questions to discuss

1. How many cities on the chart have a murder rate above the U.S. rate, and how many are below it?
2. Why does a chart like this use murders per 100,000 people instead of the total number of murders in each city?
3. A city's rank can jump from one year to the next. Why might small numbers make rates bounce around?