You can work out the likely impact of a law liberalising the market for product category x on related industries a, b, c, (etc.) and even make an educated guess about the overall impact that this law may have on the economy as a whole.
But when it comes to the economy you can never understand everything – if we’ve learned nothing else in the last 12 months, we’ve learned that. Hell, with something as complex as a continent-wide economic system, there are so many other factors at play, though it may be possible to make an educated guess about the impact of a piece of legislation (enough to judge if it’s going to be beneficial, at any rate), you’ll never be able to track *all* of its effects – countless other things will be affecting individual parts of the economy in countless different ways, from other bits of EU and national legislation (which still often overlap) through local levels of trades unionism, consumer spending patterns, passing fashions, local infrastructure, and so on and so on.
In other words, to be able to put an actual monetary figure on the costs/benefits of EU legislation *as a whole*, you’d first need to work out a system for tracking all the workings of the entire European economy (or, at the very least, the entire economy of the individual member state you want to study). Because without complete understanding how an economy works both at macro- and micro- levels, it is impossible to judge how introducing variable x might affect it – because who’s to say it’s not actually variable b, h or z instead if you haven’t also studied their influence?.
So even more than with claims about the percentages of laws coming from the EU, *any* claims about the costs OR benefits of the EU must be nonsense. Because the only way we could actually tell is if a) we understood the economy of Europe inside-out (which we don’t), and b) we had a control sample of a Europe in which the EU never came into being to which we could compare our findings. We can put a figure on how much we pay in to the EU in the form of taxes, therefore, but we can’t sensibly do the same for the wider economic benefits or costs.
So although I feel that the EU has done more good than harm to both the British economy and the economy of Europe as a whole, there is no way that I can prove that. There’s also no way that anyone of a more eurosceptic bent can prove that the opposite is true. I could point to individual benefits, they could point to individual costs – we could add up more and more of each until we have a wealth of evidence and can start chucking around figures like 200 or 600 billion. But we’d still have only scratched the surface.
This is not a flaw in the way the EU works, it is just a consequence of the EU’s continent-spanning economy (which exists in a world that has become increasingly globalised, and so increasingly economically complex and volatile over the last fifty years) being an incredibly, vastly, inconceivably complicated system that no one can ever fully understand.
It does, however, mean that arguments about the benefits and costs of the EU are always going to come down to subjective feelings, not objective truths. Chuck onto that the fact that most EU legislation is by its nature quite vague (being in the most part a compromise between disparate interest groups from 27 member states, compromised upon yet further during discussions between the European Parliament, Council and Commission), and is often implemented in vastly different ways from member state to member state, depending on the whim of the local authorities, then proving that the EU is beneficial to those who feel that it is not is, therefore, just about an impossible task.
(Modified from a comment left on this post at The Devil’s Kitchen.)