The first is one you should have heard of: opportunity cost. Many economists consider “opp cost” to be the single most important and fundamental concept in economics, and the discipline’s most useful contribution to the betterment of mankind. Indeed, that’s the view Professor John Quiggin, of the University of Queensland, takes in his book Economics in Two Lessons, which I recommend as the best book to introduce you to economics. Quiggin says “the opportunity cost of anything of value is what you must give up to get it”. Our wants are almost infinite, but our resources are limited, so we have to make choices. Economists’ eternal message to individuals and to the community is: think carefully before you spend your money, make sure you’re spending it on what you really want because you can’t spend it twice. Really? That complicated, huh? Quiggin says “the lesson of opportunity cost is easy to state but hard to learn”. We keep forgetting to apply it. For instance, Prime Minister Scott Morrison is saying he’s not going to reduce our greenhouse gas emissions if the opportunity cost is to endanger jobs in the coal industry. Sounds fair enough until you realise he’s saying jobs in a particular industry matter more to him than us doing all we can to help reduce global warming (which will destroy jobs in many industries).

Prime Minister Scott Morrison is saying he’s not going to reduce our greenhouse gas emissions if the opportunity cost is to endanger jobs in the coal industry. Credit:Matt Davidson We live in a market economy. We sell our labour in the jobs market, then use the money we earn to buy the goods and services we need in 101 product markets. Economics is the study of markets and, in particular, of how the prices set in markets work to bring supply and demand, sellers and buyers, into agreement (aka “equilibrium” or balance). 2. Invisible hand The first of Quiggin’s two lessons is “market prices reflect and [also] determine the opportunity costs faced by consumers and producers” – which brings us to Sims’ next key concept, “the invisible hand”. In a market-based economy (as opposed to a feudal economy or a planned economy), the differing objectives of workers, employers, consumers and producers are co-ordinated (brought together) not by the government issuing orders to people, but by the “price mechanism” (prices going up or down until both sides are satisfied).

That’s the invisible hand. And what motivates this invisible hand is the self-interest of workers, bosses, consumers and businesses. In the famous words of the father of modern economics, Adam Smith, in 1776, “it is not from the benevolence of the butcher, the brewer or the baker that we expect our dinner, but from their regard to their own interest”. It’s amazing to think of, but it holds much truth: the invisible hand of markets and prices takes the self-interest of all those competing players and turns it into a situation where most of us have our wants satisfied most of the time. 3. Imperfect competition But if that sounds a bit too pat – a bit too perfect – it is. It is, in fact, a description of what economists call “perfect markets” and “perfect competition”. And in real life, nothing’s ever perfect. The greatest female economist, Joan Robinson, was the first to formalise Sims’ third key concept, “imperfect competition” – the study of why markets and the price mechanism don’t always work as perfectly as the oversimplified “neo-classical” model of markets assumes they do. 4. Market failure

From the subtitle of Quiggin’s book you see that lesson one is “why markets work so well”, but lesson two is “and why they can fail so badly”. This takes us straight to Sims’ fourth key concept “market failure”. Markets are said to fail when they deliver results that aren’t “allocatively efficient” – when they don’t lead to the particular allocation of economic resources that yields the maximum satisfaction of people’s wants. Loading Economists have spent much time studying the various categories of factors that cause markets to fail. More recently they have turned to studying “government failure”, which is when governments’ attempts to correct market failures end up making things worse. 5. Externalities Sims’ final key concept is “externalities” – a major category of market failure. These occur when transactions between sellers and buyers generate costs (or benefits) for third parties – known as “social” costs or benefits – that aren’t reflected in the market or “private” prices paid and received by the buyers and sellers.