The recent “tech-stock bubble” provides us with an illustration of such a difficulty: while one was witnessing the “irrational exuberance” in 1996, the surge in capital spending associated with the development of new technologies resulted in a faster productivity growth, which in turn boosted equity prices. At that time, uncertainties about fundamentals (was there an American miracle?) made difficult a proper assessment of asset valuations, although the large movements in asset prices where a concern for central banks. However, when expectations reverse, for example due to the reassessment of expected profitability in the economy, and consequently asset prices decrease, the point is to determine whether the attitude of the central bank ought to be different in order to preserve monetary and financial stability. That is, some could argue that the central bank’s response should be asymmetric. In the booming phase, as long as price stability is not endangered, central banks do not react to the rise in asset prices. Conversely, in the recession phase or when a bubble bursts, central banks could consider reacting if they deem that monetary and financial stability is endangered. What could then restrain them from doing it?
The issue of measuring price stability However, this raises another issue, especially in the current context of muted inflationary pressures but ample fluctuations in asset prices: are we measuring inflation accurately? Is price stability being ensured, in the context of large movements in asset prices? Shouldn’t asset prices be taken into account when defining price stability? Up to now, this debate has focused on the role asset prices may play as leading indicators of inflation: one rationale behind this thinking may be that asset valuation is computed in a forward looking manner, and therefore asset prices embed expectations about future economic growth and future inflationary pressures. Empirical evidence gathered on such an issue tend to support the idea that some asset prices, housing prices in particular, may actually play such a role. However, this theory has to be qualified by the fact that, as I mentioned earlier, wealth effects are difficult to establish in a definitive manner. This is probably less true for the US, although this is debatable and could be discussed in this conference, but this is more likely to be true for the euro area. Moreover, there might be a danger that asset prices diverge from the CPI, as this was observed over the last few years. There might be an internal conflict here if the objective of price stability is defined by aggregating the changes in the CPI and the changes in asset prices, and this is a crucial issue since the nature of both types of prices is fairly different.