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 · Space
How many planets outside our solar system are discovered each year?
The interactive chart needs JavaScript. The numbers are on the chart's page.
Astronomers confirmed 246 new planets around other stars in 2025. The first were found in 1992, and the count leaped in 2014 and 2016 (872 and 1,504), when NASA's Kepler team confirmed hundreds of its candidates at once. The archive counts a planet in the year its discovery was published and keeps adding late confirmations, so recent years can still rise.
Questions to discuss
- In one sentence of your own, what does this chart show?
- Find the biggest change or difference in the chart. What might explain it?
- Who collected these numbers, and how recent are they? What else would you want to know before drawing a conclusion?
Source: NASA Exoplanet Archive, Planetary Systems Composite Data (Public domain (NASA data); this research has made use of the NASA Exoplanet Archive, operated by Caltech under contract with NASA) · Data as of Dec 31, 2025
Open the chart and its numbersChart 2 of 3 · Wealth
What is the median household net worth by age?
The interactive chart needs JavaScript. The numbers are on the chart's page.
In the Federal Reserve's 2025 survey, the typical (median) household headed by someone under 35 had a net worth of $32,820, and one headed by someone 35 to 44 had $156,000. The median was $254,670 for ages 45 to 54, $411,340 for 55 to 64, $431,900 for 65 to 74 and $504,600 for 75 and over, about 15 times the under-35s'. The median is the household in the middle: half have more and half less. Averages are much higher, because a few households are very rich. Net worth is what a household owns (homes, retirement accounts, stocks, businesses, cars, bank accounts) minus what it owes (mortgages, student and car loans, credit cards). The survey is taken every three years, and figures are in dollars of the survey year. People of different ages also lived through different times, so this compares age groups, not one household's path through life.
How to read this chart
Each bar is the median net worth of households, grouped by the age of the person who heads them. Net worth is what a household owns, such as a home, savings and retirement accounts, minus what it owes, such as a mortgage or student loans. The median is the household in the middle: half have more and half have less.
Questions to discuss
- Which age group has the highest median net worth, and about how many times the under-35 group's is it?
- Why might net worth keep rising through most of a working life, and why might it fall for the oldest group?
- A few very rich households pull the average far above the median. Why is the median a better picture of a typical household?
Source: Federal Reserve Board, Survey of Consumer Finances (Public domain (Federal Reserve Board; cite the Board as the source)) · 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
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