Of course, the effect of monetary policy on house prices is only half of the story: When considering the potential benefits of monetary policy for combatting the risk of a housing boom and ultimately for financial stability, it’s equally important to gauge the effects on other macroeconomic variables of interest, such as inflation and economic activity (Yellen 2014). In many circumstances, macroeconomic and financial stability goals may be well aligned. For example, if the housing sector and the overall economy are both booming, then tighter monetary policy may serve to both reduce the risks to the financial system and keep economic activity from exceeding desired levels. But, in other circumstances, macroeconomic and financial stability goals may conflict, and policymakers face a tradeoff between the two. As a case in point, Lars Svensson (2014) has argued that in Sweden, the costs of higher interest rates in terms of higher unemployment exceed the benefits in terms of reducing financial stability risks. Therefore, it is important to quantitatively gauge the costs and benefits of using monetary policy to influence house prices when macroeconomic and financial stability goals do not coincide.
Measuring the effects of monetary policy
The question remains: How does one best estimate the effects of monetary policy on house prices and other economic variables of interest? Economists typically take one of two approaches. The first is to use economic theory to describe the relationship between variables, say interest rates and house prices. The model can then be used to evaluate the “counterfactual” experiment of a rise in interest rates and compute the simulated effect on house prices or other variables (Dokko et al. 2009, Svensson 2014, and Ungerer 2015). The main strength of this model-based approach is that it gives a clear theoretically grounded answer to the question. The potential shortcoming is that the answer is only as good as the model is at providing a reasonably accurate description of the relationships that occur in the real world. Specifically, standard textbook theories may provide an inadequate description of the determination of house prices (Kuttner 2012). This suggests looking to a more evidence-based approach.
The second approach focuses more squarely on the empirical evidence and relies less directly on economic theory. In a nutshell, the empirical approach looks at what has typically happened to other variables when interest rates go up (or down). The strengths and weaknesses of this approach are the mirror image of those of the model-based approach. The main strength is that one does not rely so much on having an accurate model. The weakness is that it’s hard to distinguish between statistical correlation and economic causation. Interest rates go up and down in response to economic conditions and also tend to be highly correlated with other variables. However, to answer the question about the effects of a policy decision to change interest rates, it is crucial for one to properly identify times when policy changes are not a response to economic developments, but rather the driver of them.