Growth synchronisation in euro area countries

By Jaime Martinez-Martin, Lorena Saiz and Grigor Stoevsky

Published as part of the ECB Economic Bulletin, Issue 5/2018.

The degree of business cycle synchronisation, both across the euro area countries as well as between the euro area and the rest of the world, is a pertinent research question. Regarding the euro area, the endogenous optimal currency area (OCA) hypothesis^[1] suggests that the degree of business cycle synchronisation among the participating countries should increase over time as a result of deepening financial and trade integration. Individual countries should thus become less exposed to idiosyncratic shocks, facilitating the effectiveness of the single monetary policy. Against this background, this box presents and analyses several measures of business cycle synchronisation both within the euro area as well as from a global perspective.

In an environment of stronger trade and financial linkages, the favourable growth dynamics of recent years are common to the majority of euro area countries and world economies (see Chart A). Between 2014 and 2016 the share of world countries with strengthening growth declined, partly reflecting the negative impact of low oil prices on oil-producing countries. However, the share of countries with improving growth dynamics has been rising since the second half of 2016, with more than half of euro area countries experiencing a strengthening of economic dynamics. This has coincided with the broadening of economic growth that began in 2013.^[2]

Chart A

Share of countries with current GDP growth exceeding the past three-year average

(quarterly data, percentages)

The recent strengthening of growth has coincided with a broad-based reduction in growth dispersion across the euro area countries and in advanced economies (G7) (see Chart B). Growth volatility across euro area countries was very high in the aftermath of the global financial crisis as well as during the sovereign debt crisis. This implied that the impact of the shocks was very diverse across countries. In contrast, the recent decline in growth dispersion across euro area countries has largely coincided with a reduction in fragmentation in financing conditions in the euro area, facilitated by the ECB’s monetary policy measures.

Chart B

Dispersion of quarterly real GDP growth rates

(quarterly data, percentages)

A direct measure of correlation confirms that synchronicity increased among the euro area countries in 2016-17 (see Chart C). The correlation measure^[3] for the euro area^[4] suggests that the degree of business cycle synchronisation increased sharply around the time of the global financial crisis for all sets of countries considered. Among the euro area countries, and in general among the advanced economies, the correlations reached a peak during the financial crisis, and gradually declined over the recovery period. However, this measure shows that there was a renewed trend towards increased synchronisation across the euro area countries in the course of 2017. Over the last two decades, synchronisation has been higher among the largest five euro area economies relative to a broader group of 17 euro area countries, although synchronisation among the latter increased sharply in the course of 2017.^[5]

Chart C

Business cycle correlations across euro area and G7 countries

The increase in synchronisation is also evident in the fact that a substantial share of the variation in GDP growth across the euro area countries is explained by a common factor (see Chart D). The common component explains on average more than 65% of the GDP growth variance across euro area countries as well as across advanced world economies (G7). However, the share explained by the common factor increased sharply during the financial crisis owing to the synchronised downturn. It is notable that synchronisation in terms of this measure rose again in recent years in the euro area. This trend is in contrast to that observed in the G7 countries, where there is less evidence of a common factor explaining the recent cross-country variation in GDP growth.

Chart D

Relative contribution of the common factor to real GDP growth variance

(percentage of total variance)

All in all, the evidence points to a relatively high level of growth synchronisation across the euro area countries. While economic growth dynamics have strengthened recently in a larger share of euro area and global economies, this has coincided with a broad-based reduction in volatility across these major world economies. The recent increase in synchronisation across the euro area countries to relatively high levels is confirmed by both the calculated correlation index and the estimated high share of GDP growth variation explained by a common factor.