Evidence? Who needs evidence…

Economics is an “observational science”. What does that mean? It means that, by and large, its something we observe rather than something we recreate in the laboratory under controlled conditions.

Why does this matter? Because it makes strong statements about what caused what more difficult. If we can’t be sure that something else didn’t cause what we’re looking at, then that casts doubt on our proposed explanation.

This is perhaps most acute in the area of public policy, particularly when it comes to the macroeconomy. Earlier in the week the Chancellor of the Exchequer (in charge of fiscal policy) was able to make a lot of concessions to a lot of people because of better than expected growth (that’s expected to happen). But is that better than expected growth due to great fiscal policy since 2010 (as some might argue), or due to more favourable other factors (less austerity than the government wanted to do since 2010)? Or something else entirely – better growth in our trading partners? The answer to this question matters a lot, since it tells us what fiscal policy would be more effective.

It’s always interesting to draw parallels with other fields, particularly when things are topical. As you’ll be aware, at the moment there are reforms being proposed for the NHS – namely to turn it into a seven-day service from its current (supposed) non-seven day service. A huge amount has been written and said and shouted about this, but the bottom line is if you’ve ever been into hospital on a weekend you’ll know that the NHS does indeed function on weekends.

As such, the argument has switched to whether it’s more risky to have been admitted on a weekend. Two studies have been relied upon, but the problem is that these studies are based on observational data. A comment published two days ago by the British Medical Journal (BMJ) says:

1. This is an observational study and cannot determine causation.

This is, alas, true. We cannotĀ determineĀ it. We can have a bloody good go at it, nonetheless, and you’ll learn a lot in econometrics about how we can go about this. But we cannot determine it, we can only be sure of it to some degree of confidence – usually 95%.

This doesn’t nullify the use of economics as a field of study, nonetheless – there’s a lot we can understand much more clearly via further study – but it is important to keep this in mind when studying economics…