Nominal rigidity


In economics, nominal rigidity, also referred to as price stickiness or wage stickiness, describes a situation in which a nominal price is slow to adjust or resistant to change. Complete nominal rigidity occurs when a price remains fixed in nominal terms for a relevant period of time. For example, the price of a good may be contractually set at $10 per unit for an entire year, regardless of changes in supply and demand conditions. Partial nominal rigidity occurs when prices can adjust, but less than they would under conditions of perfect flexibility. For instance, in a regulated market, there may be legal or institutional limits on how much a price can change within a given year.
Nominal rigidities are considered a central feature of many Keynesian and New Keynesian models, as they help explain why markets may not always clear and why shifts in aggregate demand can have real effects on output and employment in the short run. The concepts of sticky prices and sticky wages are particularly important for understanding the effectiveness of monetary policy.
If one looks at the whole economy, some prices might be very flexible and others rigid. This will lead to the aggregate price level becoming "sluggish" or "sticky" in the sense that it does not respond to macroeconomic shocks as much as it would if all prices were flexible. The same idea can apply to nominal wages. The presence of nominal rigidity is an important part of macroeconomic theory since it can explain why markets might not reach equilibrium in the short run or even possibly the long run. In his The General Theory of Employment, Interest and Money, John Maynard Keynes argued that nominal wages display downward rigidity, in the sense that workers are reluctant to accept cuts in nominal wages. This can lead to involuntary unemployment as it takes time for wages to adjust to equilibrium, a situation he thought applied to the Great Depression.

Evidence

There is now a considerable amount of evidence about how long price-spells last, and it suggests that there is a considerable degree of nominal price rigidity in the "complete sense" of prices remaining unchanged. A price-spell is a duration during which the nominal price of a particular item remains unchanged. For some items, such as gasoline or tomatoes, prices are observed to vary frequently resulting in many short price spells. For other items, such as the cost of a bottle of champagne or the cost of a meal in a restaurant, the price might remain fixed for an extended period of time. One of the richest sources of information about this is the price-quote data used to construct the Consumer Price Index. The statistical agencies in many countries collect tens of thousands of price-quotes for specific items each month in order to construct the CPI. In the early years of the 21st century, there were several major studies of nominal price rigidity in the US and Europe using the CPI price quote microdata. The following table gives nominal rigidity as reflected in the frequency of prices changing on average per month in several countries. For example, in France and the UK, each month on average, 19% of prices change, which implies that an average price spell lasts about 5.3 months.
Country Frequency Mean Price Spell duration Data Period
US27%3.71998–2005
UK19%5.31996–2007
Eurozone15%6.6Various, covering 1989–2004
Germany10%101998–2004
Italy9%11.11996–2003
France19%5.31994–2003
Switzerland27%3.72008–2020

The fact that price spells last on average for 3.7 months does not mean that prices are not sticky. That is because many price changes are temporary and prices revert to their usual or "reference price". Removing sales and temporary price cuts raises the average length of price-spells considerably: in the US it more than doubled the mean spell duration to 11 months. The reference price can remain unchanged for an average of 14.5 months in the US data.
Also, it is prices that we are interested in. If the price of tomatoes changes every month, the tomatoes price will generate 12 price spells in a year. Another price that is just as important might only change once per year. Looking at these two goods prices alone, we observe that there are 13 price spells with an average duration of /13 equals about 2 months. However, if we average across the two items, we see that the average spell is 6.5 months /2. The distribution of price spell durations and its mean are heavily influenced by prices generating short price spells. If we are looking at nominal rigidity in an economy, we are more interested in the distribution of durations across prices rather than the distribution of price spell durations in itself. There is thus considerable evidence that prices are sticky in the "complete" sense, that the prices remain on average unchanged for a prolonged period of time. Partial nominal rigidity is less easy to measure, since it is difficult to distinguish whether a price that changes is changing less than it would if it were perfectly flexible.
Linking micro data of prices and cost, Carlsson and Nordström Skans, showed that firms consider both current and future expected cost when setting prices. The finding that the expectation of future conditions matter for the price set today provides strong evidence in favor of nominal rigidity and the forward looking behavior of the price setters implied by the models of sticky prices outlined below.

Modeling sticky prices

Economists have tried to model sticky prices in a number of ways. These models can be classified as either time-dependent, where firms change prices with the passage of time and decide to change prices independently of the economic environment, or state-dependent, where firms decide to change prices in response to changes in the economic environment. The differences can be thought of as differences in a two-stage process: In time-dependent models, firms decide to change prices and then evaluate market conditions; In state-dependent models, firms evaluate market conditions and then decide how to respond.
In time-dependent models price changes are staggered exogenously, so a fixed percentage of firms change prices at a given time. There is no selection as to which firms change prices. Two commonly used time-dependent models are based on papers by John B. Taylor and Guillermo Calvo. In Taylor, firms change prices every nth period. In Calvo, price changes follow a Poisson process. In both models the choice of changing prices is independent of the inflation rate.
The Taylor model is one where firms set the price knowing exactly how long the price will last. Firms are divided into cohorts, so that each period the same proportion of firms reset their price. For example, with two-period price-spells, half of the firms reset their price each period. Thus the aggregate price level is an average of the new price set this period and the price set last period and still remaining for half of the firms. In general, if price-spells last for n periods, a proportion of 1/n firms reset their price each period and the general price is an average of the prices set now and in the preceding n − 1 periods. At any point in time, there will be a uniform distribution of ages of price-spells: will be new prices in their first period, 1/n in their second period, and so on until 1/n will be n periods old. The average age of price-spells will be /2.
In the Calvo staggered contracts model, there is a constant probability h that the firm can set a new price. Thus a proportion h of firms can reset their price in any period, whilst the remaining proportion keep their price constant. In the Calvo model, when a firm sets its price, it does not know how long the price-spell will last. Instead, the firm faces a probability distribution over possible price-spell durations. The probability that the price will last for i periods is i−1, and the expected duration is h−1. For example, if h = 0.25, then a quarter of firms will rest their price each period, and the expected duration for the price-spell is 4. There is no upper limit to how long price-spells may last: although the probability becomes small over time, it is always strictly positive. Unlike the Taylor model where all completed price-spells have the same length, there will at any time be a distribution of completed price-spell lengths.
In state-dependent models the decision to change prices is based on changes in the market and is not related to the passage of time. Most models relate the decision to change prices to menu costs. Firms change prices when the benefit of changing a price becomes larger than the menu cost of changing a price. Price changes may be bunched or staggered over time. Prices change faster and monetary shocks are over faster under state dependent than time. Examples of state-dependent models include the one proposed by Golosov and Lucas and one suggested by Dotsey, King and Wolman.

Significance in macroeconomics

In macroeconomics, nominal rigidity is necessary to explain how money can affect the real economy and why the classical dichotomy breaks down.
If nominal wages and prices were not sticky, or perfectly flexible, they would always adjust such that there would be equilibrium in the economy. In a perfectly flexible economy, monetary shocks would lead to immediate changes in the level of nominal prices, leaving real quantities unaffected. This is sometimes called monetary neutrality or "the neutrality of money".
For money to have real effects, some degree of nominal rigidity is required so that prices and wages do not respond immediately. Hence sticky prices play an important role in all mainstream macroeconomic theory: Monetarists, Keynesians and new Keynesians all agree that markets fail to clear because prices fail to drop to market clearing levels when there is a drop in demand. Such models are used to explain unemployment. Neoclassical models, common in microeconomics, predict that involuntary unemployment should not exist, as this would lead employers to cut wages; this would continue until unemployment was no longer a problem. While such models can be useful in other markets where prices adjust more readily, sticky wages are a common way to explain why workers cannot find jobs: as wages cannot be cut instantaneously, they will sometimes be too high for the market to clear.
Since prices and wages cannot move instantly, price- and wage-setters become forward looking. The notion that expectations of future conditions affect current price- and wage-setting decisions is a keystone for much of the current monetary policy analysis based on Keynesian macroeconomic models and the implied policy advice.
Huw Dixon and Claus Hansen showed that even if only part of the economy has sticky prices, this can influence prices in other sectors and lead to prices in the rest of the economy becoming less responsive to changes in demand. Thus price and wage stickiness in one sector can "spill over" and lead to the economy behaving in a more Keynesian way.