The Air Got Cleaner While the Economy Grew, and the Numbers Show How

Try to imagine the headline: "Air Cleaner Than It Was When Your Parents Were Young, Experts Report." You cannot, because nobody would click it, and nobody would pay a reporter to write it. Good news about the environment is the one story that comes with no villain and no deadline for a donation, so it runs in the back, if it runs at all.

That silence matters, because the argument over environmental policy rests on an assumption that the record does not support. The assumption is that a growing economy and a clean environment are at war, so that every gain in one is paid for by a loss in the other. If that were true, the last half century of American history should show dirty air getting dirtier as the country got richer. It shows the reverse.

Define the terms. The criteria pollutants are the six common air pollutants for which the Environmental Protection Agency sets national air quality standards under the Clean Air Act: particulate matter, ground-level ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide and lead. Aggregate emissions means the combined tonnage of the pollutants, as tracked by EPA's long-running trend reports, which the agency publishes under the title Our Nation's Air. A trend is a comparison across years, which is the only honest way to say whether something is improving.

The claim: since 1970, the combined emissions of the common air pollutants have fallen by roughly three-quarters while the economy, the population and the miles Americans drive all grew. Prosperity and clean air are not enemies. In this case, the first paid for the second.

The numbers, with the arithmetic shown

EPA's trend reports, which anyone can read on its website, compare the period beginning in 1970 with a recent year. In its recent editions, the agency's headline is that aggregate emissions of the six common pollutants fell by about 78 percent over the five decades from 1970. Over the same period the report records that gross domestic product, adjusted for inflation, grew several-fold, that the population grew by well over half, and that the miles driven by American vehicles more than doubled. I give the pattern and not decimal places because the exact percentages move from one edition of the report to the next, and you should check the latest edition before quoting a figure in a debate. What does not move is the direction: emissions down, everything else up.

Let me show why the combination is more striking than either number alone. Take an index, set at 100 for 1970 for both emissions and economic output. The numbers below are an illustration of the arithmetic using round figures near the ones in the report, not a quotation of any single year.

• If aggregate emissions fall by 78 percent, the index drops from 100 to 22.
• If the economy grows to four times its 1970 size, its index rises from 100 to 400.
• Emissions per unit of output are then 22 divided by 400, which is 0.055, against 1.0 at the start.
• The drop in emissions per unit of output is 1.0 minus 0.055, or 0.945, which is a fall of about 94.5 percent.

The exact multiple for the economy is a matter for the report, and a growth factor of three instead of four would give a result near 93 percent instead. Either way the point survives: the amount of pollution that comes with a dollar of output has collapsed. A country that produces four times as much while polluting a quarter as much has not traded one for the other. It has found out how to have both.

This is what a conservative should expect. Economic growth is not a pile of identical widgets. It is a rise in what we can do with a given input, and a good part of that is the ability to do the same job with less waste. The catalytic converter, the scrubber on a smokestack and the cleaner-burning fuel are goods that wealth makes affordable.

Four stories behind the line

A trend line does not clean anything. People do. Here are the four chapters that account for most of the movement.

Lead

For much of the twentieth century, most gasoline contained lead, added to keep engines from knocking, and the lead went out the tailpipe and into the air and the soil. Lead is a toxin that harms the developing brains of children, and its effects were established well before the law caught up. Under the Clean Air Act of 1970 and the EPA, which Congress and the Nixon administration created that year, the government began restricting leaded gasoline, beginning with the arrival of catalytic converters that cannot run on it. The phase-out was gradual, and the sale of leaded gasoline for on-road vehicles ended entirely in 1996.

The result is among the sharpest drops in the whole record. Lead in the air fell by an enormous percentage, and the reduction of lead in children's blood followed. Whatever else you say about the regulators of that era, this one worked, and it is fair to say so. Conservatives should be the first to say it, since a policy that stops a manufacturer from poisoning the neighbors is just what the common law's protection of person and property would require.

Acid rain

In the 1980s, sulfur dioxide from coal-burning power plants was blamed for acid rain, which damaged lakes and forests in the Northeast and Canada. The Clean Air Act Amendments of 1990, signed by President George H. W. Bush on November 15, 1990, took a new approach in Title IV of the law. Rather than ordering each plant to install particular equipment, Congress set a national cap on total sulfur dioxide emissions from power plants, handed out allowances equal to the cap, and let plants trade them. A plant that could cut emissions cheaply could sell its spare allowances to one that could not. The overall cap was set to bring emissions roughly ten million tons below their 1980 levels.

It worked, and it worked more cheaply than most people predicted. This is the policy that conservative and free-market economists had been recommending for years: set the goal, let the market find the cheapest way to meet it. The government decided how much pollution was acceptable and left the how to the people who knew their own plants. If you want a model of environmental policy that respects both the air and the price system, you have it. A cap-and-trade system for a specific, measurable, local pollutant is a very different animal from the sprawling schemes proposed for carbon dioxide, a distinction that matters when the next proposal arrives with the same name.

Cars

The tailpipe of a modern passenger car emits a tiny fraction of the smog-forming pollutants that its 1970 ancestor did. Catalytic converters, fuel injection, onboard computers and cleaner fuels did that, driven in part by regulation and in part by competition among automakers. The miles driven went up and the emissions per mile went down by so much that the total fell. This is the clearest case of the pattern in the report: the number of cars, the miles on them and the pollution from them moved in different directions.

The factory and the power plant

Scrubbers, filters and better combustion cut particulate and sulfur emissions from industrial sources. The shift from coal to cheap natural gas in electric power, which happened for economic reasons and not on a government timetable, cut them further. The story of how that gas came to be plentiful is in How America Went From Importing Natural Gas to Shipping It Worldwide, and it is worth noticing that the cleanest chapter in the electricity business was written mainly by the drillers the political class likes least.

Why wealth buys clean air

There is a reason the pattern holds, and it is an old one in economics. Economists who study pollution have found, in many data sets, that as a country begins to industrialize its pollution tends to rise, and that after incomes pass a certain level, pollution falls. The relationship, often drawn as an upside-down U, is known as the environmental Kuznets curve, after the economist Simon Kuznets, who described a similar shape for inequality. It is not a law of nature. Some pollutants follow it and some do not, and it did not make a policy unnecessary. It describes a tendency: the first thing a poor family wants is food, the second is a roof, and clean air becomes something they can afford to demand after those are secured.

The 1970 Clean Air Act did not come out of nowhere. It came out of a country rich enough to ask for more than a paycheck. That has a consequence for the poorest countries, which cannot yet afford to clean their air in the way ours is, and it reminds us that the surest long-term way to clean air is to get wealthy first, which is the argument of Hundreds of Millions Still Cook Over Wood, and That Is a Moral Question.

It has a second consequence at home. Regulations are easier to pass and to bear in a growing economy. A rule that costs a plant a million dollars is a nuisance for a firm in a boom and a death sentence for one in a slump. The 1970s, a decade of stagnation, taught that lesson painfully. The point is not to skip regulation. It is to remember that the ability to pay for it is not free, and that the wealth is the source of the budget.

The strongest objection

The best case for the opposing view should be stated fairly.

The best case: The air improved because of regulation, not because of wealth. Left alone, factories and utilities would have kept polluting, because the cost of pollution falls on the neighbors and not on the polluter. The Clean Air Act gave government the power to set standards, and without it we would not see the decline. Prosperity did not clean the air. The law did, and it did so against the opposition of industry. Rolling back such rules in the name of growth would reverse the gains.

Here is the response, point by point.

1. Regulation helped, and I have said so. Lead, acid rain and tailpipe standards are all cases where law drove the result. The claim is not that the market alone cleaned the air. The claim is that the law and the growth worked together, and that the supposed tradeoff between them did not appear.
2. The best of the regulation was the kind that sets a goal and lets people find the way. The acid rain cap-and-trade program is the model. The worst regulation tells each plant what equipment to buy. Conservatives are not against clean air. They are against paying more than necessary for it, which is also what a family does at the grocery store.
3. The objection proves the point about wealth. A law like the Clean Air Act passes in a society that can afford it and wants it. The same law in a poor country would not hold. The two explanations are partners.
4. The key question is the next rule, not the last one. The easy gains, the big ones from lead, from sulfur and from the dirtiest tailpipes, have been taken. Each further cut costs more than the last. A rule that was a bargain in 1975 may not be in 2025, and the honest test is cost against benefit, rule by rule. Pointing at the old victories does not justify a new rule any more than pointing at a good meal justifies a second dinner.
5. A rule has to be made by the people who answer to voters. A law written by Congress can be debated and repealed. A standard written by an agency under a broad delegation is harder to hold to account. The Supreme Court in 2022 held in West Virginia v. EPA that an agency claiming vast regulatory power over a major part of the economy needs clear authority from Congress. That is not an attack on clean air. It is an argument that Congress should vote.

Why you do not hear about it

If the numbers are this good, why does so little of it reach the public? I will not cite a poll, because I do not have one I can source. But it is a fair observation that the coverage points the wrong way.

Think about the incentives. A story that says a city's air is better than it was forty years ago is not a story. A story that says a chemical has been found somewhere is. Environmental groups raise money by raising alarm, and an organization whose whole case is that the problem is solved has made itself unnecessary. Politicians who want a bigger program need a bigger problem. And reporters, like everyone else, are rewarded for what bleeds. None of this requires a conspiracy. It requires only that everyone follow his incentive, which is a thing conservatives understand better than most.

The effect is a population that is afraid of the wrong thing. It is the same pattern described in Hot Day Means Climate Crisis, Cold Snap Means Weather, a Lesson in Coverage, in which the same weather becomes a different story depending on the headline someone wants. If the air is cleaner, say so. A movement that cannot admit success will never know when to declare victory, and a movement that never declares victory is a lobby.

The Founders and the common law

Where does a conservative stand on all this? On firm ground.

The Constitution does not mention air, but the principle behind clean air is older than the Constitution. The common law of nuisance has long held that you may not use your property in a way that harms your neighbor's. A factory that fills a neighbor's yard with soot is committing a wrong the courts recognized for centuries before there was an EPA. John Locke wrote that each man has a property in his own person and labor, and a man who poisons the air his neighbor breathes violates it. The rule of law protects the individual from the pollution of others as surely as from the tyranny of kings.

What the Founders would not have recognized is a delegation so vast that an unelected agency sets the terms of the whole economy. Article I, Section 1 says "All legislative Powers herein granted shall be vested in a Congress of the United States." The right way to have clean air is a law passed by Congress, applied by courts, measured by honest numbers and revisited when the numbers change. That is how the 1990 acid rain program worked, and it is why it is the model. You can see the broader catalog of regulations that Washington writes on the page that tracks red tape.

The conservative conservationist tradition runs the same way. Theodore Roosevelt protected land and water through law and public argument, as Theodore Roosevelt Made Conservation a Conservative Cause, and It Still Is describes. A man who loves the outdoors need not apologize for loving clean air as well.

The case in brief

1. EPA's trend reports show aggregate emissions of the six common air pollutants down by about 78 percent since 1970, while output, population and driving all grew.
2. With illustrative round numbers, emissions of 22 against output of 400 give emissions per unit of output of 0.055, a fall of about 94.5 percent. Clean air and growth are not enemies.
3. The big gains came from lead removed from gasoline by 1996, the acid rain cap-and-trade program of 1990, cleaner cars and cleaner power plants, and the best of them set a goal and let the market find the cheapest way.
4. Wealth buys clean air, as the environmental Kuznets curve suggests, and the next rule must be judged by cost against benefit and passed by Congress.
5. The good news gets little coverage because it offers no villain and no fundraising letter, which is a reason to say it louder.

What you can do: look up your county's air quality trend on EPA's website, then ask your member of Congress which air rules were voted on and which were written by the agency.