Consumption Against Numbers

In one line

Environmental pressure is the number of people multiplied by what each of them consumes, and the second term varies far more between people than the first varies between countries.

In the wording a student can write in an exam: the consumption argument holds that total environmental impact is a product of population, affluence and technology, so that a small population consuming heavily can place a greater demand on the biosphere than a large population consuming little. It follows that a policy directed at numbers alone addresses the term that varies least, and the international instruments have adopted this position: Rio Principle 8 requires States to reduce and eliminate unsustainable patterns of production and consumption and to promote appropriate demographic policies, in that order, and Goal 12 of the Sustainable Development Goals is about consumption and production while no Goal concerns population size.

The identity

The argument is usually stated as an identity, and it is worth setting out because it makes the structure visible.

Impact is population multiplied by affluence multiplied by technology. Population is the number of people. Affluence is consumption per person, usually measured as goods and services consumed. Technology is the environmental impact per unit consumed, which falls as processes get cleaner and rises as they get dirtier.

Three consequences follow.

All three terms matter, so an argument that any one of them is the whole problem is wrong on its face.

Reducing one term can be offset by another. A halving of impact per unit is cancelled by a doubling of consumption per person, which is the rebound effect and is the standard objection to relying on efficiency alone.

And the terms are not equally movable. Population responds slowly and to instruments with high constitutional cost. Consumption and technology respond to price, regulation and product standards, which are ordinary legal instruments.

The evidence

Consumption per person varies enormously. The difference in energy, water and material use per person between the richest and the poorest countries is of an order that no difference in fertility approaches.

Emissions illustrate it. As the chapter on air and energy sets out, India's total emissions are large and its per capita emissions are well below the world average, and its cumulative contribution is smaller still. A country's population tells you very little about its contribution until you know what its people consume.

And within a country the same is true. The wealthiest households in any country, India included, consume many multiples of what the poorest do, which is why the argument is a domestic one and not only an international one.

What the instruments say

Rio Principle 8. To achieve sustainable development and a higher quality of life for all people, States should reduce and eliminate unsustainable patterns of production and consumption and promote appropriate demographic policies.