When Gigi Foster gave a radical speech to the Economic Society in Sydney last week – which soon had the audience interjecting and arguing among itself – she was careful to begin by saying her goal was to add to the standard economic model, not replace it.
She claimed the economists' model was the most successful model in all of social science, then listed what she considered to be its four most useful contributions.
By rights I should be telling you about her radical additions to the model, but I'll save that for another day because I, too, have been known to be fairly full and frank about the model's weaknesses and, like her, I don't want anyone thinking that means I regard it as a load of bulldust.
Just the reverse, in fact. It's been so useful and so influential that most of its insights will strike you as bleeding obvious. They are now.
Dr Foster, an associate professor at the University of NSW, is one of Australia's leading behavioural economists. Along with Professor Paul Frijters, of the University of Queensland, she's the author of the ground-breaking book, An Economic Theory of Greed, Love, Groups and Networks.
Her first "big hit" of conventional economics is its discovery that there are "gains from trade". And what's true within an economy – where we each specialise in producing something we're good at, then use money to trade with others – is equally true between economies.
It follows that countries preferring self-sufficiency to the interdependency of international trade will forgo much prosperity. One of economics' earliest discoveries is the benefit of "comparative advantage": countries do best when they concentrate on producing those things they can make at least opportunity cost relative to other countries' opportunity costs.
So you avoid erecting barriers to trade, follow your comparative advantage and import the rest from the cheapest suppliers.
Foster's second big win for economics is realisation of the benefits of competition – not just between producers but also between producers and their customers. So we prevent or regulate monopolies. We create markets when none exist – by, for instance, putting a price on carbon.
And we intervene in markets where we see that competition isn't sufficient to prevent them from failing to deliver the benefits we expect and where the intervention is likely to make the market work better.
Third, a natural role for governments is the provision of "public goods" – goods or services whose nature prevents private producers from capturing enough of the benefits to induce them to provide as much of the item as is in the community's interests.
Examples of public goods provided by governments are numerous: infrastructure, defence, education, the system of law and even the currency.
Foster's final example is the finding that monetary incentives matter. People respond to price changes – though their degree of responsiveness or "elasticity" varies under the influence of other factors. Taxation discourages economic activity, leading to a "deadweight loss" to the community.
That's Foster's list of insights we owe to economists and their model, but I can think of a few more. One is the aforementioned concept of opportunity cost. Because economic resources – including environmental assets – are limited, anything we choose to do comes at the cost of everything else we can't do with those resources.
Since these other things are endless, economists measure opportunity cost by looking only at the next most desirable thing we could have done. The moral of opportunity cost is: since you can't have everything, choose carefully.
Another insight is that anything we choose to do will bring costs as well as benefits. Moral: be sure to weigh the costs against the benefits before you jump.
Then there's our tendency to look only at the initial effect of particular developments. Economists know to ask the next question: but then what happens? It's usually the reaction to the initial effect – the "second-round effect" – that matters.
Say there's a big rise in the cost of electricity. The initial effect is to leave you with less money to spend on other things, which you hate. So you react to this by using power less wastefully, by buying a more energy-efficient fridge next time, or by investigating the costs and benefits of installing solar panels.
All this may seem obvious, but that's a measure of the economists' success in influencing the way we think.
Even so, it's surprising how often we forget these things. That's why we need economists as well as their model: to keep reminding us of the seemingly obvious and doing what they can to stop us wasting money.
