Speech: The Economics of Human Extinction - 21 May 2026

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Speech: The Economics of Human Extinction - 21 May 2026

Posted by Andrew Leigh 2sc on

The Hon Andrew Leigh MP<br>Assistant Minister for Productivity, Competition, Charities and Treasury

The Economics of Human Extinction

Giblin Lecture,<br>University of Tasmania

Thursday, 21 May 2026

1. The Last Externality

I acknowledge the muwinina people, the traditional and original owners of the land on which we gather tonight, and pay my respects to Tasmanian Aboriginal people and to First Nations people present. My thanks to Mark Bowles, the University of Tasmania and the Tasmanian branch of the Economic Society of Australia for organising this event.

As a longtime admirer of Lyndhurst Giblin, it is an honour to be delivering the 2026 Giblin lecture. Giblin was born in 1872, exactly 100 years before me. He was both a Labor member of parliament and a professor of economics (Cain 1981). He loved Tasmania’s high country, and I like to think that in the modern era, his passion for exercise and mountains would have made him a keen ultramarathoner.

At this point, I can almost imagine we belong in the same paragraph. But not when you note that Giblin also played Rugby Union for England, prospected for gold in Canada and taught ju-jitsu in London. In the First World War, Giblin fought at the Somme and Passchendaele, was wounded three times, and received the Distinguished Service Order.

As an economist, Giblin focused on large, practical questions. How to manage an economy in crisis? How to design institutions that would endure? He did early work on what became known as the Keynesian multiplier, shaped the approach of the Commonwealth Grants Commission and helped form the Economic Society of Australia.

Giblin did not confine himself to tidy questions. He worked on problems that mattered, even when they were messy or uncertain. He belonged to a generation of economists who did not wait for perfect data before offering advice, perhaps because the problems they faced did not wait either.

That makes him an apt namesake for a lecture on a topic that economists have largely neglected: the risk that the system does not merely falter, but ends.<br>Economists are comfortable analysing recessions, financial crises, floods, fires and wars. We estimate output losses and calculate distributional effects. These are large shocks, sometimes very large shocks. But they share a feature that is so familiar we rarely name it: recovery is possible. Output falls, then rebounds. Populations suffer, then rebuild. The future continues. This talk is about a different class of risk. Not the risks that make humanity poorer or sicker, but the risks that could permanently end humanity.

Earth’s history reminds us that extinctions happen. Over the past half-billion years, life on our planet has been shaken by at least five mass extinction events, each wiping out a large share of species. The dinosaurs had a 160-million-year run; then their luck ran out.

Here, extinction means the complete loss of our species. No survivors, no recovery, no second act. One estimate, from Australian philosopher Toby Ord, puts the odds of such a catastrophe at one in six over the coming century (Ord 2020; Ord 2024a). Surveys of experts have come up with similar figures (Newberry 2021).

These possibilities have long been the domain of philosophers. In recent years, they have also become the subject of empirical and scientific inquiry. What has been missing is a clear economic framing.

That absence is surprising. Economics is about choice under scarcity. Yet the discipline has said relatively little about the ultimate scarcity: the possibility that there may be no future over which to make choices at all.

The stakes are almost incomprehensibly large. Our species is only a few hundred thousand years old, while the sun has billions of years left to burn. Roughly 100 billion humans have lived so far. If humanity endures, the number who might yet live could reach into the trillions, with one estimate suggesting that there could be a billion billion future people for every person who has ever lived (Newberry 2021). Humanity may still be in its infancy. If so, extinction would mean more than the loss of those alive today: it would foreclose all the human lives that might otherwise come after us (Leigh 2021).

The risks are rising. Past earth extinctions were caused by natural events, such as climate fluctuations and asteroid strikes. Today, the most significant risks are anthropogenic – the ones our species has brought upon ourselves. In the twentieth century, nuclear weapons and catastrophic climate change made that possibility immediate. Emerging technologies, such as advanced artificial intelligence and synthetic biology, may extend it further.

Economists’ neglect of the topic of human extinction reflects something about how our discipline tend to think. The standard tools of economics are well...