Blog Post

Is the economy stationary?

What’s at stake: The question of whether capitalist economies are self-correcting and will eventually revert to mean growth has received renewed interest given the underperformance of most economies six years after the onset of the Great Recessions. While the idea of persistent high unemployment was central to Keynes’ General Theory, it was quickly abandoned by the neoclassical synthesis.

By: Date: May 18, 2015 Topic: European Macroeconomics & Governance

Tyler Cowen writes that the most crucial issue is whether economies will return to normal conditions of steady growth, or whether we are witnessing a fundamental transformation, unveiled in bits and pieces. One relatively optimistic view is that observed deficiencies — like slow growth in real wages and the overall economy, persistently low interest rates and low levels of labor participation — are merely temporary.  Another commonly heard view is that we made the mistake of letting the last recession linger too long, allowing some of its features to become entrenched.

Unit roots, random walks and stationary series

John Cochrane provides a simple illustration of the different concepts. Suppose there is an unexpected movement in a series. How does this “shock” affect our best estimate of where this variable will be in the future? The graph shows three possibilities. First, green or “stationary.”  There may be some short-lived dynamics. But, given enough time, the variable will return to where we thought it was going all along. Second, blue or “pure random walk.” If the price goes up unexpectedly, your expectation of where the (log) price will be in the future goes up one-for-one, for all time. Third, black, “unit root.” This option recognizes the possibility that a shock may give rise to transitory dynamics, and may come back towards, but not all the way towards your previous estimate. As you can see the “unit root” is the same as a combination of a stationary component and a bit of a random walk.

Source: John Cochrane

John Cochrane writes that the pure question whether the series will come back in an infinite time period is not really knowable. It could be that the series will come back eventually, but take a very long time. It could be stationary plus a second very slow moving stationary component. This is a statistical problem but not really an economic problem. The appearance of unit roots are economically interesting as they show a lot of “low frequency” movement, series that are coming back slowly – even if they do come back eventually.

History of an idea: high unemployment as a persistent equilibrium

Roger Farmer writes that classical economists from David Hume, through to Adam Smith, David Ricardo and John Maynard Keynes’ contemporary, Arthur Pigou, viewed the economy as a self-regulating mechanism. In the third edition of his undergraduate textbook, Samuelson replaced Keynes’ notion, of high unemployment as an equilibrium, with a new idea: the neoclassical synthesis. According to that idea, the Keynesian high unemployment equilibrium is only temporary. It applies in the short run, when prices and wages are sticky, but in the long run, when all wages and prices have had time to adjust, the economy reverts to a classical equilibrium with full employment.

Roger Farmer writes that Keynesians and monetarists adopted the Phillips curve as the missing equation that explains the transition from the short run to the long run. If the neoclassical synthesis is correct then the economy will always return to full employment as wages and prices adjust to clear markets. Unemployment cannot differ permanently from its natural rate and Keynes’ original vision of high unemployment, as a persistent steady state, must be fatally flawed.

The data: stationary or not?

Arnold Kling writes that if you think of the economy as ultimately self-correcting, then what it corrects to is potential GDP. If the economy is not self-correcting, then the concept of potential GDP can have no objective basis.

Roger Farmer writes that there is no evidence the economy is self-correcting. If, as Robert Gordon believes, it is caused by random technology shifts then there is not much that monetary policy or macro prudential policies can do about it. If, however, it is caused by random movements from one inefficient equilibrium to another, we should be thinking very hard about how to design a monetary/macro-prudential policy that keeps the economic train on the tracks.

John Cochrane writes that the “unit root” is most plausible and verified in the data for log GDP. Recessions and expansions have a lot of transitory component that will come back. But there are permanent movements too. Unemployment, being a ratio, strikes me as one that eventually must come back. But it can take a longer time than we usually think, which is interesting.

Paul Krugman writes that clearly, models with rational expectations, markets continuously in equilibrium, and unique equilibria don’t cut it. But which pieces of such models would you want to modify or replace? Farmer wants to preserve rational expectations and continuous equilibrium, while introducing multiple equilibria. That strikes me as a bizarre choice. Why not appeal to behavioral economics, behavioral finance in particular, to make sense of bubbles? Why not appeal to the clear evidence of price and wage stickiness — perhaps grounded in bounded rationality — to make sense of market disequilibrium?

 


Republishing and referencing

Bruegel considers itself a public good and takes no institutional standpoint. Anyone is free to republish and/or quote this post without prior consent. Please provide a full reference, clearly stating Bruegel and the relevant author as the source, and include a prominent hyperlink to the original post.

View comments
Read article More on this topic More by this author

Blog Post

Demographics and Long Run Growth

Scholars have been investigating the relationship between demographics and long term growth, in the context of the secular stagnation hypothesis. We review recent contributions.

By: Silvia Merler Topic: Global Economics & Governance Date: June 18, 2018
Read article More on this topic More by this author

Blog Post

The Italian mini-BOT debate

Talks of parallel currency are not new in Italy. But one of the proposals – the so called mini-BOT – has made it into the government contract that underpins the current League-M5S coalition. We review what has been said about these proposals.

By: Silvia Merler Topic: Finance & Financial Regulation Date: June 11, 2018
Read article More on this topic More by this author

Blog Post

The Italian Crisis

While Italy has been through one of the gravest institutional crises in its history, we review recent opinions on the topic.

By: Silvia Merler Topic: European Macroeconomics & Governance Date: June 4, 2018
Read article More on this topic More by this author

Blog Post

China’s new role in the global economy

The changing role of China in the world economy has recently been highlighted by its registering of a first current account deficit in 17 years. We review the economists’ analyses of this new role and associated challenges.

By: Nicolas Moës Topic: Global Economics & Governance Date: May 28, 2018
Read article More on this topic More by this author

Blog Post

Argentina’s troubles

Argentina has abruptly called on the International Monetary Fund for financial help, amid currency pressures. We review recent economists’ position on this.

By: Silvia Merler Topic: Global Economics & Governance Date: May 22, 2018
Read article More on this topic More by this author

Blog Post

200 Years of Karl Marx

May 5th 2018 marked the 200th anniversary of the birth of Karl Marx. We review some economists’ takes on the controversial philosopher’s legacy.

By: Silvia Merler Topic: Global Economics & Governance Date: May 14, 2018
Read article More on this topic More by this author

Blog Post

Did Economics Fail?

The debate about rethinking economics keeps rambling. We summarise newest contributions to this important discussion.

By: Silvia Merler Topic: Global Economics & Governance Date: May 7, 2018
Read article More on this topic More by this author

Blog Post

The cost of remittances

Remittances flows are very important for developing countries. In 2009 the G8 pledged to reduce the cost of remittances to 5%, a commitment that was endorsed by the G20 in 2011 and 2014, and included in the UN’s Sustainable Development Goals in 2015. What is the cost today, and what are economists’ suggestions to reduce it?

By: Silvia Merler Topic: Global Economics & Governance Date: April 30, 2018
Read article More on this topic More by this author

Blog Post

Trade Wars: what are they good for?

Following the US announcements in early March of their intent to impose steel and aluminum tariffs, and the subsequent threats from China to retaliate with their own tariffs, the global trade picture remains uncertain. The IMF and the World Bank Spring Meetings set off amid US-Japan bilateral negotiations and Trump’s hot-and-cold approach to the TPP. This week we review blogs’ views on tensions over international trade and how they can impact world economic growth.

By: Inês Goncalves Raposo Topic: Global Economics & Governance Date: April 23, 2018
Read article More on this topic More by this author

Blog Post

The debate on euro-area reform

A paper jointly written by 14 French and German economists set off a debate about the reform of euro-area macroeconomic governance. We review economists’ opinions about it.

By: Silvia Merler Topic: Finance & Financial Regulation Date: April 16, 2018
Read article More on this topic More by this author

Blog Post

Latvia’s money laundering scandal

Latvia’s third largest bank ABLV sought emergency liquidity from the ECB and eventually voted to start a process of voluntary liquidation, after being accused by US authorities of large-scale money laundering and having failed to produce a survival plan. What does it mean for the ECB?

By: Silvia Merler Topic: Finance & Financial Regulation Date: April 9, 2018
Read article More on this topic More by this author

Blog Post

Milton Friedman's " The role of monetary policy" - 50 years later

In March 1968, Milton Friedman’s “The Role of Monetary Policy” - after his famous presidential address to the American Economic Association - was published in the American Economic Review. 50 years later, economists reflect on this famous work.

By: Silvia Merler Topic: Global Economics & Governance Date: April 3, 2018
Load more posts