Book review: The Bet by Paul Sabin

For Christmas my brother-in-law gave me The Bet by Paul Sabin. Here’s my review. You can find other reviews by googling.

Sabin is a history professor at Yale. The Bet is a popular (but fully footnoted and sourced) account of a famous bet between ecologist Paul Ehrlich and economist Julian Simon over whether the real (i.e. inflation-adjusted) prices of five widely-used metals would rise or fall over the 1980s. Ehrlich thought they would rise because human population growth would lead inexorably to resource scarcity. Simon thought they would fall because the combination of free markets and human ingenuity would lead to the development of either new sources or substitutes. Simon won. Sabin places the bet in the context of the US environmental movement of the 60s and 70s, particularly concern about overpopulation, and the subsequent conservative pushback. At the end, he argues that both Ehrlich and Simon, and the movements they helped inspire and lead, failed to appreciate the good points of the other side. Instead, the political debate became too personal, polarized, and extremist to be useful. This degraded the ability of the American government to address serious environmental problems, including climate change, and degraded the ability of American society to have a serious conversation about what sort of world we want to live in.

I liked the book and recommend it. It’s a quick read—I knocked it off in a few hours. It’s engaging—lots of personal background and anecdotes about Ehrlich and Simon.* And I learned a lot. I came into the book knowing only the broad-brush potted history of the environmental movement, and Ehrlich’s role in it.** But while I now know more, the fact that I don’t have many other sources to draw on besides The Bet means that I’m not well-positioned to identify any serious flaws in it. So take everything I say with a grain of salt.

Some hopefully-interesting thoughts inspired by the book:

  • As with any history book, part of the fun is putting yourself in a different mindset. Hard as it may be to believe now, a few decades ago human population size was well under half of what it is today–and yet human population growth was one of the big issues of the day.
  • I came into the book with the vague sense that Ehrlich was basically right (or at least closer to right than Simon was), that he was unlucky to lose the bet, and that events like east African famines illustrate Ehrlich’s basic rightness. I left it thinking that Ehrlich was basically wrong. Ehrlich’s claims were much more specific and extreme than just “humans are having a big effect on the planet and this creates some serious problems that we need to address”. Of course, Simon had his own blind spots, especially as his own position grew more extreme (and frankly, odd). I like Cass Sunstein’s characterization of the Ehrlich-Simon clash as “a clash of two hedgehogs“. If you want to think sensibly about human population growth and its consequences, I think you’re much better off with Joel Cohen’s How Many People Can the Earth Support? than with anything by Ehrlich or Simon.
  • I myself have dealt in a small way with the same problem faced by Ehrlich, Simon, or any activist. To get people to pay attention to what you have to say, you often have to say it in an attention-grabbing way. In my case, by making zombie jokes. But the same rhetoric that gets people’s attention also can make them less likely to agree with you.
  • You can’t always map in any simple way from someone’s experiences growing up to their professional views as adults. But in this case, it sounds like you can (assuming that Sabin isn’t slanting the biographical material in order to jam Ehrlich and Simon into tidy boxes). Ehrlich always loved butterflies and lonely wilderness, and was viscerally repulsed by the crowded cities he visited in India. In contrast, Simon always liked the bustle of city life. I suspect this is what a lot of heated debates, in and outside science, come down to—disagreements about deep-seated preferences and values. Witness the current fight in conservation biology over whether we should conserve nature for its own sake, or for our sake—it’s a fight even among people who agree that nature should be conserved! It’s really hard to have a productive discussion about deep-seated values, or to have a political process that functions well despite the participants disagreeing deeply about values. Which is why I was disappointed in Sabin’s call at the end for a nuanced debate about how humans should live in a world with rapid anthropogenic climate change. He sounds like he’s wishing for a pony, because he doesn’t say anything about how one might create (recreate?) the conditions under which an urgent debate is possible without getting dominated by extreme voices. Easy for me to talk, of course, since I don’t have an answer here either.
  • I was interested to read quotes from Ehrlich and his collaborators saying explicitly that their goal wasn’t to win a reasoned argument. The goal was to use any means necessary—including “alarmism” (their word) and insulting their opponents—to attract attention, set the political agenda, and change government policy. Obviously, there are lots of ways for scientists to get involved in politics besides Ehrlich’s way. But if you want to know what it looks like for a scientist to go “all in” in pursuit of a policy goal, read this book and find out.
  • It’s striking that Ehrlich and Simon both tried to bolster their political position by claiming that objective science was totally on their side, and that the other side was just ignorant of basic, obvious “facts”.
  • At one level, the bet was pointless—the outcome was never going to prove anything about the consequences of human population growth. On the timescale of a decade (or even much longer), commodity prices in both nominal and real terms depend totally on macroeconomic forces, not on human population growth (which is why the fact that Ehrlich would’ve won the bet in the majority of other 10-year periods for which we have data is irrelevant). But on another level, the bet does illustrate that Ehrlich was wrong. Timescales and timing matter. Foreseeing global famine and worldwide collapse of human society within, say, a couple of decades is very different than foreseeing them, say, centuries from now. And it’s not helpful to predict a global disaster at some indeterminate point in the future, as Ehrlich did in the aftermath of the bet. In the long run we’re all dead. Yes, insurmountable physical or biological constraints of some sort will bite at some point—Simon’s later claim that the human population could keep growing exponentially for 7 billion years is silly, there’d be more humans than atoms in the universe at that point. But saying “Some insurmountable physical or biological constraint will bite at some point” is no guide at all to policy—it’s far too vague, except perhaps as an added reason to undertake policies that would be a good idea anyway. And saying “I’m still right, my prediction just hasn’t come true yet” is just a way of absolving yourself from admitting error.
  • I have an old post extolling the value of betting your beliefs, on the grounds that bets force you to be precise and explicit. Thereby removing your wiggle room to rationalize and obliging you to recognize your mistakes and thus learn from them. That may work in contexts where people aren’t personally invested in the outcome of the bet. But as the aftermath of the Ehrlich-Simon bet illustrates, nothing can make a true believer admit error and give up his core beliefs, especially not when doing so would only hand a further political victory to his opponents. Ehrlich paid out on the bet—but subsequently claimed that the bet was on matters of “marginal importance”, and that he was “schnookered” into taking the bet in the first place (no he wasn’t). And his collaborator John Holdren claimed that he and Ehrlich were never making predictions and so it didn’t matter if they were right or wrong. Rather, they were merely raising possibilities (never mind that, if you’re merely raising possibilities, you don’t bet on them coming true.)***
  • It’s telling that Ehrlich and Simon tried and failed to agree a second bet. Ehrlich wanted a new bet on trends in environmental variables like atmospheric CO2 concentration and tropical forest area, while Simon wanted to bet on trends in variables directly related to human health and wellbeing, like life expectancy. Their failure to agree a second bet nicely illustrates that what was always at stake here was values, not empirical claims.
  • Human population growth apparently was the issue for Ehrlich, but it was interesting to read about how he ended up taking stances on lots of other issues too, based on purported links to human population growth. For instance, he got into a lot of political trouble arguing that the US should severely restrict or eliminate immigration, because immigrants to the US would consume resources at the high per-capita rates typical of Americans. This was interesting to me, because it contrasted with my mental image of people with a single-issue focus as not caring about other issues. Single-issue politics of Ehrlich’s sort has two obvious drawbacks as a political approach. First, you have to convince people that one issue really is of overriding importance, so that it should dictate our stances on all other issues. That seems difficult except in wartime. This is well illustrated by Ehrlich’s fight with fellow environmentalist Barry Commoner over whether human population growth was even an issue at all. Second, you end up picking counterproductive fights with people who don’t agree with your stance on other issues. I think the same points crop up in other contexts, including scientific ones (e.g., some debates over open access publishing).
  • On the other hand, in highlighting the downsides of Ehrlich’s approach to politics, I wonder if Sabin isn’t missing some things. For instance, if you really do think human society faces an imminent existential threat and that the only chance of survival is to make all sorts of radical policy changes, then it makes sense to try to maximize the (necessarily small) chance of making those radical changes happen. And even if your goal is more incremental policy change, there might be times when getting incremental change means arguing for radical change. Perhaps in order to reach the sky, you have to aim for the stars. Sabin notes that environmentalism in the 1970s had a lot of big political successes, but at the end he kind of implies that those successes could’ve happened without folks like Ehrlich taking radical stances. I’m not sure. For instance, what if radicals widen the Overton window, the range of possible policies that get seriously considered rather than dismissed out of hand? By publicly discussing extreme policies****, radicals might widen the Overton window. There’s a fine line to walk here, obviously—advocate for something too extreme and you risk getting dismissed as a nutter and making less-extreme views also seem nutty by association, narrowing the Overton window rather than widening it. But obviously, it’s really hard to do counterfactual history and say how much political success the environmental movement would’ve had in the 1970s with a different mix of political tactics.

I bet (haha) that many of you also have read The Bet, or haven’t but have interesting thoughts nonetheless. Looking forward to reading your comments.

*The coolest of which was learning that it was Julian Simon’s idea to have airlines offer money to passengers who volunteered to be bumped from overbooked flights. Previously, they used to just bump people involuntarily.

**Just as an aside, I’ve never met or corresponded with Ehrlich or anyone else who crops up in the book.

***Of course, as Noah Smith points out, people might take a bet for all sorts of reasons besides their beliefs about whatever that particular bet is about. So while Sabin thinks that Ehrlich was sincerely betting his beliefs, one could certainly imagine him taking the bet for other reasons instead of or in addition to that. Say, as just one more way of attracting media attention.

****For instance, Ehrlich refused to rule out the possibility of mass forced sterilizations (!), though he stopped short of arguing for them.

15 thoughts on “Book review: The Bet by Paul Sabin

  1. Thinking like an ecologist, it is inevitable to assume that the human population will sustain a tremendous crash. It is the fate that befell lynxes, lemmings, and so many others before. Interestingly, it is only education and technological development that transforms human populations from exponentially increasing ones (like in most of Africa) to slowly declining ones like almost all advanced industrial nations (all of Europe, Japan, the US and Canada) If I were asked to predict the future, I’m afraid that what’s in store for us is – both. Developing countries with unstable governments will suffer catastrophic loss of life. The stable, industrial west will continue to be just that.

    • “Thinking like an ecologist, it is inevitable to assume that the human population will sustain a tremendous crash.”

      Don’t overgeneralize from Ehrlich to all ecologists. There were ecologists at the time who thought Ehrlich was way off base. Joel Cohen’s an ecologist. I’m an ecologist and I cringed to read Ehrlich saying that every species undergoes boom-bust dynamics, the implication being that humans will to (in fact, only a small minority of species exhibit high-amplitude population cycles).

  2. Thanks for the thought-provoking review. In a similar vein – and perhaps a bit closer to the experiences of many ecologists – I can recommend “The Idea of Biodiversity” by David Takacs (1996). It is based on lengthy interviews with ~20 leading ecologists and conservation biologists (including Ehrlich, and also E.O. Wilson, Jane Lubchenco, Michael Soulé, Thomas Lovejoy, among others), and it explores the inevitable tensions that arise at the intersection of deeply felt personal values, science, and a desire to effect political change. There’s not quite as much drama as a public wager, but it’s fascinating to learn how different people navigate this tricky terrain. For some, the goal has been, as Jeremy stated, “to use any means necessary… to attract attention, set the political agenda, and change government policy”. One can’t help but wonder about associated costs to the credibility of science.

    • Thanks very much for that Mark, I should probably be embarrassed that I’d never heard of (or have totally forgotten) that book.

      Am thinking of doing a post on “forgotten books that ecology students really should read”. Will have to add that to the list–and get around to reading it myself! The original inspiration for the post was a comment here from some ecology grad student in a top grad program, thanking another commenter for pointing out Foundations of Ecology because he’d never heard of it. I was surprised by this comment, I had naively assumed that reading Foundations was pretty routine for ecology grad students.

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  4. Just came across this recent, brief commentary by two eminent ecologists:

    *Very* much in the spirit of Ehrlich, I think. Note in particular the lament at the end that a global one child policy would be unenforceable thanks to the forces of “greed and competition”, and the suggestion that our choices are to decrease global population in a planned way or to let “wars, poverty and pandemics” do it for us. Note also the earlier claim that everything from political unrest in the Middle East, to oil price “volatility”*, to the US housing bubble and subsequent slow economic recovery, are due to “interacting limits and feedbacks”, an impending “global tipping point” in the “Earth’s life support systems”.

    *a difference from Ehrlich, actually–he’d have said “increase” rather than “volatility”. I leave it to others to evaluate the claim that both increases *and* decreases in the real price of oil (i.e. volatility) are harbingers of an impending global crisis.

  5. In fairness to Ehrlich (and Hochberg and Brown, in the link in my previous comment), I just realized that I once made an *exactly* parallel argument with respect to the reviewer tragedy of the commons: There are signs here and there that the system is under pressure, and the inexorable logic of the tragedy of the commons says that the pressure’s only going to get worse. And we don’t want to wait until after the system collapses to come up with a solution (and I didn’t say what would constitute “collapse” or when it would occur, but I implied that it would be bad enough, and happen soon enough, to be worth taking immediate, very costly action). The solution will necessarily be coercive, because that’s the only way you solve tragedies of the commons. Hence we should be talking right now about implementing PubCreds (i.e. we should be talking about how to force authors to review 2 papers for every one they submit; see

    Looking back, I was wrong. I tried to make a case for revolution, when really the evidence and arguments only made a case for evolution. What I should’ve said (and did say to some extent, but should’ve emphasized much more) was something like the following. There are signs the peer review system is coming under pressure, and reasons to think it’ll come under more pressure. Which fortunately creates incentives for people to innovate and invent ways to relieve that pressure (e.g., PeerJ: I really have no precise idea what the future holds. But it seems like it’d be useful to get some data on how much pressure the system is under (which I did eventually do: And it’d be useful to discuss the pros and cons of a wide range of different ways of dealing with whatever problems there are.

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