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 · 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 numbersChart 2 of 3 · Income and poverty
What is the typical household income in each state?
The interactive chart needs JavaScript. The numbers are on the chart's page.
In the Census Bureau's 5-year survey ending in 2024, the typical household in District of Columbia earned $109,870 a year, the most, followed by Massachusetts ($103,960) and Maryland ($103,678). Mississippi was lowest at $56,447, and the U.S. median was $80,734. These are 5-year estimates in 2024 dollars, each with a margin of error.
How to read this chart
Each bar is the median household income in a state: half of households earn more and half earn less. The dashed line is the whole U.S., for comparison. These are survey estimates, and each has a margin of error: the true value is likely within that range, so states with overlapping ranges may not really differ.
Questions to discuss
- Find your state. Is it above or below the U.S. median, and by about how much?
- Why do statisticians often use the median instead of the average (mean) for income?
- Housing and groceries cost more in some states. What would you need to know to compare what these incomes can buy?
Source: U.S. Census Bureau, American Community Survey 5-year estimates (Public domain (U.S. government work). This product uses the Census Bureau Data API but is not endorsed or certified by the Census Bureau.) · Data as of Dec 31, 2024
Open the chart and its numbersChart 3 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
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