A tiny shift can matter at population scale. Demo bell curve: baseline mean 100, shifted mean 98 55 70 85 100 115 130 145 IQ score Population density Additional people below threshold Fewer people above threshold Baseline mean: 100 Shifted mean: 98 Small shift large population effect Prototype only: approximate curves for visual testing

Start with the distribution.

A bell curve helps show why small average changes can matter across a whole population.

First, the baseline.

The black curve represents a standard distribution with an average score of 100.

Then shift the mean.

The red curve is shifted left by 2 IQ points. The move looks small near the centre.

But the tail changes.

The shaded area shows the additional people below the lower threshold after the mean shifts left.

The other tail changes too.

The shaded area shows the people who would have been above the upper threshold before the population shifted left.

The meaning is scale.

The individual shift may seem tiny. Across millions of people, the consequences become visible.