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The Yield Curve, June 2007

Since last month, the yield curve has steepened considerably, with short rates falling and long rates rising. As a consequence, the yield curve is no longer inverted. That is, long rates are once again higher than short rates. One reason for noting this is that 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 six recessions (as defined by the NBER ). Very flat yield curves preceded the previous two, and there have been two notable false positives: an inversion in late 1966 and a very flat curve in late 1998. More generally, though, a flat curve indicates weak growth, and conversely, a steep curve indicates strong growth. One measure of slope, the spread between 10-year bonds and 3-month T-bills, bears out this relation, particularly when real GDP growth is lagged a year to line up growth with the spread that predicts it.

Yield Curve Spread and Real GDP Growth
Yield Curve Spread and Lagged Real GDP Growth

The yield curve had been giving a rather pessimistic view of economic growth for a while now, but with the inversion gone, this is less pronounced. The spread has turned positive: With the 10-year rate at 5.20 percent and the 3-month rate at 4.66 percent (both for the week ending June 15), the spread stands at 54 basis points, up a lot from May's -23 basis points. Projecting forward using past values of the spread and GDP growth suggests that real GDP will grow at about a 2.3 percent rate over the next year. This prediction is on the low side of other forecasts, in part because the quarterly average spread used here remains negative.

Predicted GDP Growth and the Yield Spread

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 a recession in the next year is 15 percent, down a quite a bit from Mays's value of 35 percent and April's 38 percent. The 15 percent is close to the 16.9 percent calculated by James Hamilton over at Econbrowser (though to be fair we are calculating different events: Our number gives a probability that the economy will be in recession over the next year. Econbrowser looks at the probability that the quarter fourth quarter of 2006 was in a recession).

Probability of Recession Based on the Yield Spread

Of course, it might not be advisable to take this number quite so literally, for two reasons. 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 CommentaryDoes the Yield Curve Signal Recession?

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