How does the trade balance relate to economic activity? The graph above shows the U.S. trade balance for goods and services as a percentage of GDP. Obviously, there was a surplus initially and now there’s a persistent deficit. Beyond that, it looks like every time there’s a recession, the trade deficit tends to decrease. (Or, if we go farther back in the past, the trade surplus tends to increase.) Obviously, many things affect the trade balance, but let’s see what FRED can show us about this relationship.
A good way to reveal how series may be correlated is to look at scatter plots. Instead of relating economic data to dates, scatter plots relate two data series to each other, one on each axis. The graph above does this with changes to the trade balance ratio on one axis and percent changes to real GDP on the other axis. What may look like a random assortment of dots actually has some information. Imagine the graph is divided into four quadrants and then consider where the dots are located. The upper right and lower left quadrants have fewer data points than the other two, highlighting that there is indeed a negative correlation: That is, when real GDP tends to increase, the trade balance tends to decline—that is, trade surpluses decrease or trade deficits increase.
Why is that? First, consider that the trade balance is net exports—that is, exports minus imports. Imports are highly correlated with GDP, while exports are less so. We see this in the graph above, which plots imports. This time, the upper left and lower right quadrants are the most populated. This highlights the positive correlation: That is, when real GDP tends to increase, imports do as well. Thus, over the business cycle, it is really imports that drive the trade balance: When the economy is doing well, producers need more intermediate goods, and imports are mostly intermediate goods. Also households consume more, and a share of those consumption goods are imports. If you graph exports, the correlation is much harder to see. Exports depend much more on what happens abroad, which isn’t that well correlated with domestic activity.
How these graphs were created: First graph: Search for “net exports” and select the quarterly series. From the “Edit Graph” panle, add GDP and apply formula a/b*100. Second graph: Use the first graph and change the sample period to start in 1954. From the “Edit Graph” panel, change the units to “Change.” Add a line by searching for “real GDP,” change its units to “Percent change,” open the “Format” tab, and switch the type to “Scatter.” Third graph: Use the second graph but with real imports in percent change.
Suggested by Christian Zimmermann.