Chart assignment
Charts to read and discuss
Read each chart, then answer its questions. Every chart shows its source and date; open it for a table of the numbers and the data to download.
Chart 1 of 3 · Earthquakes
How much rarer is each step up in earthquake magnitude?
The interactive chart needs JavaScript. The numbers are on the chart's page.
In 2025 the world recorded 6,428 earthquakes of magnitude 4.5 to 4.9, 1,983 of magnitude 5, 129 of magnitude 6, 15 of magnitude 7 and 1 of magnitude 8 or more. Each step up in magnitude is roughly ten times rarer, and releases about 32 times more energy. Countless smaller quakes go unrecorded worldwide, so the chart starts at 4.5.
How to read this chart
Each bar counts the earthquakes recorded worldwide in one year within a range of magnitudes. The bars start at zero. Each whole step up in magnitude releases about 32 times more energy, so a magnitude 7 quake is far more than one step stronger than a 6.
Questions to discuss
- Roughly how many times more common is each band than the one above it?
- The biggest bars are hard to compare with the smallest ones on this scale. What other way could you show these numbers?
- The chart starts at magnitude 4.5. Why might smaller earthquakes around the world go uncounted?
Source: U.S. Geological Survey, ANSS Comprehensive Earthquake Catalog (ComCat) (Public domain (U.S. government work); source U.S. Geological Survey) · Data as of Dec 31, 2025
Open the chart and its numbersChart 2 of 3 · Crime
Which big U.S. cities have the highest murder rates?
The interactive chart needs JavaScript. The numbers are on the chart's page.
In 2025 St. Louis, MO had the highest murder rate of the 89 biggest U.S. cities whose police reported a full year to the FBI, about 51.3 per 100,000 people, followed by Memphis, TN (31.0) and Cleveland, OH (28.0). Irvine, CA (0.0) and Plano, TX (0.7) had the lowest; the U.S. rate was about 4.4. Departments that didn't report a full year are left out (for 2025, New Orleans, Orlando and St. Petersburg, Florida). Each rate is per person the department serves, and a few, such as Las Vegas, Honolulu, Jacksonville and Louisville, serve their whole county. A city's rate also depends on where its borders fall, so compare cities with care.
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
- How many cities on the chart have a murder rate above the U.S. rate, and how many are below it?
- Why does a chart like this use murders per 100,000 people instead of the total number of murders in each city?
- A city's rank can jump from one year to the next. Why might small numbers make rates bounce around?
Source: FBI Crime Data Explorer, Uniform Crime Reporting Program (Public domain (U.S. government work); source FBI Uniform Crime Reporting Program) · Data as of Dec 31, 2025
Open the chart and its numbersChart 3 of 3 · World
How has the world's population grown since 1960?
The interactive chart needs JavaScript. The numbers are on the chart's page.
The world had 8.22 billion people in 2025, about 2.7 times the 3.02 billion of 1960. It passed 8 billion in 2023. Figures are mid-year estimates from the United Nations, which revises them as new censuses come in.
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
- Judging from the chart, about how many years did it take the world to add its most recent billion people?
- Is the line getting steeper or flatter in recent years? What does that tell you about the growth rate?
- These numbers are estimates that the UN revises. Why is it hard to count every person on Earth?
Source: World Bank, World Development Indicators: Population, total (CC BY 4.0 (credit the World Bank)) · Data as of Dec 31, 2025
Open the chart and its numbersTeachers: make your own chart assignment, or change this one. Free, no account needed.