Why is Everyone Talking About the Sahm Rule This Season?
The Sahm Rule has been a hot topic lately, as it allegedly signals that we are in a recession. What is the Sahm Rule and why has it become so popular? Developed by Claudia Sahm, a macroeconomist who worked at the Federal Reserve and the White House Council of Economic Advisers, the Sahm Rule is supposed to be an effective economic indicator.
It is said to signal the early stages of a recession by observing a specific shift in unemployment rates. A recession may be indicated when the three-month moving average of the unemployment rate rises by at least 0.5 percentage points above its lowest point in the prior 12 months.
The current unemployment rate is around 4.8%, by our calculations, which is historically comparatively low. The percentage of unemployment has remained at higher numbers even during long periods of economic buoyancy.
But this metric does not measure unemployment itself, rather it measures the rate of change in unemployment, or more simply, the steepness of the unemployment curve. Therefore, it works on the assumption that when unemployment is rising rapidly, rather than by absolute numbers, it is very probable that it will continue to rise at high speed, eventually getting to elevated absolute unemployment. That is the reason why some economists do not rely on the Sahm index, arguing that unless unemployment itself does not rise, the rate of change is not decisive.
With the recent BLS unemployment rate revision for August, the Sahm index peaked at 0.53, just over the 0.5 threshold. The Sahm Rule has proven reliable since 1960, with the index never rising above 0.5 without a recession in progress.
We must clarify that the Sahm Rule does not signal the start of an economic downturn, but rather marks the early stages of one, meaning that once the index goes above 0.5, a recession is already underway. The reason it cannot be used to pinpoint the beginning of a recession is because in the past recessions have always begun when the index is well below 0.5. For instance, during the last three cyclical recessions in 1991, 2001, and 2008, the Sahm index was at 0.07, 0.3, and 0.4 respectively when each recession began.
Therefore, although the Sahm rule is an indicator which has been empirically accurate since the 1960's, it does not mean, as many think, that we are entering a recession and that we should prepare for it, but rather that it already started, possibly a while ago, and that it might worsen.
The Sahm rule cannot tell how severe a recession might be, or how much it will last, as all past recessions have been distinct in both respects. Severity and duration of a recession are essential knowledge for successfully weathering it, yet they cannot be conveyed by this indicator. Thus, it appears that even though a very popular and ubiquitous indicator, it is not all-encompassing.