The lure of DIY economics
Samuel Brittan calls it businessmen's economics. David Henderson, long an international civil servant, prefers DIY economics. Both refer to propositions that people who have practical knowledge but no qualifications in economics hold to be self-evident, but which are false. Countries would do better to export more and import less. New technology destroys jobs, and public spending on my projects not only helps me but creates jobs. Manufacturing is more important than other forms of economic activity. Business would benefit from lower interest rates. People who would pause before expressing opinions in quantum mechanics or undertaking brain surgery have no hesitation in pronouncing on the economic consequences of the euro.
DIY is not confined to economics and carpentry. There is DIY medicine and even DIY physics. Common sense tells us that heavier objects fall faster, the sun revolves round the earth and the kitchen will be cooler if you leave the refrigerator door open. But experience is often misleading if we are not trained to interpret it.
It is true that light objects such as feathers fall to the ground slowly, but we mistakenly infer a general rule. And we see the sun rise in the east and set in the west. It is so obvious that the sun circles the earth that people who denied it used to be burnt at the stake. But we only observe part of the solar system. When you study the interactions of moving planets you realise that orbits around the sun are a much more compelling way of understanding the universe. And when you open the fridge door, you can feel the cold air. What you do not see is the chain of consequences. The compressor works continuously to maintain the inside temperature, and the heat it ejects from the back of the fridge offsets the cold at the front.
Scientific research and formal education are needed to understand complex systems. We learn little about the economy by being consumers and producers, just as we do not become expert in aerodynamics as plane passengers. The fallacies of DIY economics are mostly the result of generalisation: we mistakenly infer the properties of the whole from our limited experience of a smaller part.
Because every currency purchase must be matched by a sale, reducing imports effects exchange rates and the output of other producers, just as opening the fridge door alerts the thermostat and triggers the compressor. New technology may displace labour from individual jobs, but it enhances prices and profits and so increases demand for both the products of new technology and unrelated goods. Interest rate cuts would be good for business if their only effect was to reduce borrowing costs. But there are many more extensive consequences of interest rate changes, and that is why setting monetary policy is a challenging task.
The complex range of goods and services we need is the product of our interdependent economy. Are the brakes of a car more important than the engine? To ask the question is to display profound ignorance of the automobile as complex system.
Airline passengers can usefully comment on the comfort or discomfort they experience, but they do well to leave the design of the plane to aeronautical engineers. Businessmen can helpfully describe the effects of interest or exchange rates on their own business, but that defines the limit of what they can knowledgeably say.
Galileo climbed the leaning tower, not because he needed to check how quickly a lead weight would fall, but because it was the only way to convince the sceptical merchants of Pisa that gravity was not a purely theoretical construct. DIY economics persists, like DIY medicine, because there are rarely definite connections between causes and effects. If you get better after taking the snake oil, no one can tell whether it was the snake oil or whether you would have got better anyway. Physicists have opportunities for decisive experiments; doctors and economists rarely have the chance. But even Galileo could not persuade the inquisitors to look through his telescope, because ideology told them that what he claimed to see could not be there. It is a familiar experience in economic matters.
自助经济学的诱惑
塞缪尔#布里坦（Samuel Brittan）称之为商人经济学。长期在国际组织担任公职的大卫#亨德森（David Henderson）则倾向于自助经济学的说法，这两种说法说的都是那些貌似正确，实属大谬的观点，持这些观点的是非经济学科班出身，但有实际知识的那些人。这些观点包括：一个国家的出口多多益善，进口则越少越好。新技术会造成失业。如果用公共开支来支持我的项目，不仅有利于我，还会创造工作机会。生产比其它形式的经济活动更重要。低利率有利于商业。有些人你要是让他对量子力学或者脑部手术发表见解，他们会三缄其口；但是说起欧元的经济后果，他们却毫不迟疑，说得头头是道。
自助的不仅仅是经济学和木工。现在还有自助医学，自助物理学。常识告诉我们，重物下落更快；太阳绕着地球转；把冰箱门打开会降低厨房温度。但是经验这东西我们如果没有经过专门训练，了解如何阐释的话，往往会受到它的误导。
确实，羽毛等物落到地上速度很慢，但如果我们由此推断出普遍规律，那就会犯错误。我们看到太阳从东边起山，从西边下山，因此，太阳应该是绕着地球转的。这好像是明摆着的道理，持否定观点的人甚至为此上了火刑柱。但是我们只是观察到了太阳系的局部。当你研究行星之间的互动关系时，你会发现行星绕着太阳转是更为合理的宇宙观。如果你打开冰箱门，你会感到凉风从中出来。但是你没有看到接下来的连锁反应。冰箱的压缩机必须持续运转，以保持里面的温度，压缩机从冰箱后面排出热气，与冰箱前面出来的冷气相互抵消。
理解复杂的系统，我们需要有科学研究和正规教育。仅仅作为消费者和生产者，我们对经济的了解还只是皮毛。这就如同我们常乘坐飞机，但并不会因此成为空气动力学专家。自助经济学的谬误多半是概括所致：我们的阅历只是有限的局部，却会由此错误地推断关于全体的特征。
因为每当发生货币购买都必须有相应的销售，减少进口则会影响汇率和其它生产商的产量，正如打开冰箱门则对自动调温计发出信号，进而引起压缩机的相应活动。新技术或许会导致某些岗位人员的下岗，但是它改善了价格，提高了利润，因此会增加对新技术产品和其它非相关产品的需求。降低利率如果只有降低借贷成本这一个结果，那么它对商业是有好处的。但是利率的变化会有更为广泛的影响，所以制定财政政策是很有挑战性的任务。
当今产品与服务名目复杂，这是相互依存的经济造成的结果。汽车的刹车是否比引擎更为重要？问这种问题说明提问者对汽车这一复杂系统是多么无知。
飞机的乘客通常都能评论其乘机经历是愉快还是不愉快，但是飞机设计的问题，他们最好还是让航空工程师们去操心。商人不妨描述利率或者汇率变化对自己的企业有何影响，但他们所能说的也仅此而已。
伽利略爬上比萨斜塔，并不是因为他要查验铅球下落速度的快慢，而是因为这是他要性将信将疑的比萨商人们证明，地心引力并不是纯粹理论化的概念。自助经济学和自助医学一样，总是久盛不衰，其原因是因果之间很少有必然的联系。如果你用了蛇油，没有人能告诉你到底是蛇油发挥了作用，还是你自然而然康复了。物理学家还有机会做实验，通过实验一锤定音；医生和经济学家很少有这样的机会。但是连伽利略也无法说服询问者去用他的望远镜去观看，因为意识形态告诉他们，伽利略说他所看到的东西是不可能存在的。经济学上的问题，与伽利略的情形何其相似！
