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.

  1. How many clinical trials start each year?
  2. How much rarer is each step up in earthquake magnitude?

Chart 1 of 2 · Clinical trials

How many clinical trials start each year?

The interactive chart needs JavaScript. The numbers are on the chart's page.

About 31,100 clinical trials registered on ClinicalTrials.gov started in 2025, up from about 11,900 in 2008 and 1,900 in 2000, the registry's first year. Early years count fewer trials because registering wasn't required until medical journals asked for it in 2005 and a U.S. law did in 2007; late registrations still add a few to recent years. ClinicalTrials.gov lists trials from around the world, not only the U.S.

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?

Source: ClinicalTrials.gov (U.S. National Library of Medicine), counted with its API v2 (Public domain (U.S. government work); source National Library of Medicine) · Data as of Nov 4, 2026

Open the chart and its numbers

Chart 2 of 2 · 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

  1. Roughly how many times more common is each band than the one above it?
  2. The biggest bars are hard to compare with the smallest ones on this scale. What other way could you show these numbers?
  3. 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 numbers

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