The Yield Curve, June 2010
Since last month, the yield curve has dropped slightly, with both long and short rates ticking down. The difference between these rates, the slope of the yield curve, has achieved some notoriety as a simple forecaster of economic growth. The rule of thumb is that an inverted yield curve (short rates above long rates) indicates a recession in about a year, and yield curve inversions have preceded each of the last seven recessions (as defined by the NBER). In particular, the yield curve inverted in August 2006, a bit more than a year before the current recession started in December 2007. There have been two notable false positives: an inversion in late 1966 and a very flat curve in late 1998.
More generally, a flat curve indicates weak growth, and conversely, a steep curve indicates strong growth. One measure of slope, the spread between ten-year Treasury bonds and three-month Treasury bills, bears out this relation, particularly when real GDP growth is lagged a year to line up growth with the spread that predicts it.
Since last month, the three-month rate has dropped to 0.09 percent (for the week ending June 18) from May’s 0.17, and this also comes in below April’s 0.16 percent. The ten-year rate dropped to 3.26 percent from May’s 3.33 percent, also down from April’s 3.85 percent. The slope increased a mere 1 basis point to 317 basis points, up from May’s 316 basis points, but still below April’s 369 basis points.
Projecting forward using past values of the spread and GDP growth suggests that real GDP will grow at about a 1.00 percent rate over the next year, just up from May’s prediction of 0.98 percent. Although the time horizons do not match exactly, this comes in on the more pessimistic side of other forecasts, although, like them, it does show moderate growth for the year.
While such an approach predicts when growth is above or below average, it does not do so well in predicting the actual number, especially in the case of recessions. Thus, it is sometimes preferable to focus on using the yield curve to predict a discrete event: whether or not the economy is in recession. Looking at that relationship, the expected chance of the economy being in a recession next June rises to 12.4 percent, up from May’s 9.9 percent and April’s 7.1 percent, despite the slight rise in the spread. Recent data has shifted the predicted value upward, though it still remains low.
Of course, it might not be advisable to take these number quite so literally, for two reasons. (Not even counting Paul Krugman’s concerns.) First, this probability is itself subject to error, as is the case with all statistical estimates. Second, other researchers have postulated that the underlying determinants of the yield spread today are materially different from the determinants that generated yield spreads during prior decades. Differences could arise from changes in international capital flows and inflation expectations, for example. The bottom line is that yield curves contain important information for business cycle analysis, but, like other indicators, should be interpreted with caution.
For more detail on these and other issues related to using the yield curve to predict recessions, see the Commentary “Does the Yield Curve Signal Recession?”