A single snapshot of who has what can look fixed. Real life is not a snapshot. Things get better, get worse, stall, and sometimes do all three depending on which years you look at.

Today you will plot the same set of figures two ways and watch the story change. Your job is not to pick a favourite chart. It is to say what each shape does and does not tell you.

A trend is the general direction a set of figures takes over time: up, down, or roughly flat. It is not a prediction. A line on a chart only describes what already happened in the years you included.

Three traps, short form:

1. A trend is not destiny. A falling line does not promise next year will be lower.
2. The years you choose are part of the claim. Start in a bad stretch and finish in a good one, and almost anything looks like progress.
3. A smooth line hides the bumps. Real years jump. The best-fit line is a summary, not the full truth.

You are about to plot real figures on how many people worldwide lack enough food. Same source, two windows. Use the years and percentages on the board exactly as written. The traps above get proved when the shape flips.

Use the interactive with the board figures below (year and % without enough food).

Data to plot (same for both rounds):

• 2005 → 14%
• 2007 → 13%
• 2010 → 11%
• 2013 → 10%
• 2015 → 9%
• 2017 → 8%
• 2019 → 9%
• 2021 → 9%

Round 1 (whole class): together, plot only 2005, 2007, 2010, 2013 and 2015. Turn on the trend line. In one sentence, what is this line saying?

Clear the plot before Round 2. Check the chart is empty, then replot.

Round 2 (on your device): plot only 2015, 2017, 2019 and 2021. Turn on the trend line again. What is this line saying?

Both windows use the same source. In pairs, finish the board stems: “Round 1 is fair when the claim is about ___; it leaves out ___.” and “Round 2 is fair when the claim is about ___; it leaves out ___.”

Talk this through as a class. Nothing to type or save.

• When is each window the honest one to show somebody, and what would you ask before you trust any trend about who lacks enough food?

Today you learned that a trend only describes the years on the chart, not the future and not the years left out. You plotted the same figures on people without enough food in two windows and watched the shape change from a clear fall to a stall. You practised saying what each shape does and does not tell you, which is how you read a rate over time without being led by somebody else’s crop of years.