Kerby Anderson

Today is Earth Day. I was a participant in the first Earth Day as a high school student and remember one equation. It was I=PAT. The environmental impact (I) was equal to the population (P) multiplied by affluence (A) multiplied by technology (T). In other words, as a country grew in population and affluence and technology, the worse the pollution and environmental impact. The obvious conclusion was that the best way to protect the planet would be to have fewer people, less wealth, and simpler technology.

It was an interesting equation, but it turned out to be wrong as countries got richer. John Tierney pointed this out in his column in The New York Times. He acknowledges that the “IPAT theory may have made intuitive sense, but it didn’t jibe with the data that has been analyzed since that first Earth Day.” Researchers instead found that the graphs of environmental impact with a simple upward-sloping line were wrong. Instead, it turns out that the line flattens out and then slopes downward. This is called a Kuznets curve.

Here’s the trend: as countries get richer, they have more incentive and more financial means to clean up pollution. Of course, there are exceptions (especially with countries with inept governments and a poor system of property rights). But the general rule is that as incomes go up, people focus on pollution.

Tierney says: “As their wealth grows, people consume more energy, but they move to more efficient and cleaner sources — from wood to coal and oil, and then to natural gas and nuclear power, progressively emitting less carbon per unit of energy.”

I think this suggests a positive environmental future for developing countries. They may be ascending the Kuznets curve right now, but may soon be ready to address environmental concerns.