It’s that time of year again. Just as we are enticed with the possibility of a great British summer, students up and down the country are heading to their books in preparation for exams. Having the “right” pen is suddenly a matter of crucial importance, and not having a full set of highlighters is just plain silly. As exam fever heats up the question of how much revision we should be doing becomes more and more prevalent. There always seems to be someone who is working harder, revising better, with snazzy flash cards and fancy posters. However, arguably the most powerful rule in economics, the law of diminishing returns, suggests that doing too much revision is inefficient, or worse still counter-productive.
The law of diminishing returns states that in every single productive process, if all other factors are held constant, adding more of one factor will at some point lead to lower per unit returns. Diminishing returns can also often become negative returns. A common application of the law of diminishing returns is to think of employing more workers in a factory. At first more workers will lead to greater output, but once a significant number of people are being employed, additional workers will add less to marginal output. Eventually, a point may be reached where employing additional workers leads to a lower output, so-called negative returns. This occurs when there are so many workers that they are getting in each others way, knocking things over and halting the production process.
So what does this have to do with revision? Well, we can think of hours worked and grades achieved as being positively correlated. Most people would accept that more work leads to better grades. In this framework we say that factors like intelligence are exogenous (outside) the model. The diagram at the top of this article illustrates the situation. At first doing a few hours of work adds a lot to exam grades. However, soon diminishing returns set in and each additional hour of work adds less and less to your final grade. In this hypothetical model I have argued that the point (a) can be reached, where negative returns set in and additional hours of work lead to poorer exam performance. Exogenous factors like intelligence will shift the curve, so if you suddenly got dramatically smarter before exams the curve would shift up with the same hours of work leading to higher grades.
This model can be thought of in relation to all the revision you do for a module, or the work you do in one day. When I start revising I find the first hour of every day is always by far the most productive. The second hour is still good, but I’m not confidently understanding everything like I was before. By the third hour I’m starting to make silly mistakes, and once the fourth or fifth is reached it’s becoming difficult to tell whether I’m absorbing any material or just confusing my brain with multiple economics diagrams. I’m sure it’s a similar experience for most people; the law of diminishing returns is seemingly unavoidable when it comes to revision.
The law of diminishing returns can also be applied to the time spent answering exam questions. The first 60% of the marks for each question are relatively easy to get compared to the work you will have to do to go from 60% to 70%. Therefore, it makes sense to ensure an equal amount of time is spent answering all the questions, rather than writing a perfect 1st class answer for the first one, leaving yourself barely any time to get the marks for the remaining questions.
So as you sit down ready to get moving with your revision make sure you take into account the law of diminishing returns. There is such a thing as too much work. In fact pulling all-nighters in the library may actually lead to worse, not better, exam performance. Once you’re faced with the dreaded exams, make sure to remember the law of diminishing returns – especially if you’re an economics student. One final disclaimer: if you ease off because of this article and fail, I accept no responsibility.