Showing the Difference Between Correlation and Causation

BoingBoing guest blogger David Ng, a teacher of science literacy, posted the following illustration, which he uses to explain hypothesis-generation to his students.

The setup for the illustration is that a country has experienced a decline in its human birthrate and stork population at the same time, and the students are asked to think of a hypothesis to explain it.

The obvious thing to infer is that the two declines are related... since storks bring babies, of course. But that would be jumping to conclusions. Some alternate hypotheses:



Thanks, David!