The Sahm Rule: Real-Time Recession Indicator Explained

The Sahm rule is the cleanest real-time recession indicator in the modern US business-cycle toolkit. It was developed by economist Claudia Sahm in 2019 while she was at the Federal Reserve, and is now published monthly by the Federal Reserve Bank of St Louis as FRED series SAHMCURRENT. The rule triggers a recession signal when the three-month moving average of the US unemployment rate rises 0.50 percentage points or more above the lowest three-month average from the prior twelve months. As of April 2026, the indicator stands at 0.47, just below the 0.50 trigger threshold. The rule has triggered before or coincident with every NBER-dated US recession since 1970 in backtesting.

The rule's value comes from its real-time character. NBER dates recessions retrospectively, typically 6 to 18 months after the cyclical peak, once data revisions have settled and the broader six-indicator framework can be applied with confidence. The retrospective character of NBER dating is appropriate for the methodological care it represents, but it is unhelpful for policy responses that need to be triggered when a recession is starting, not confirmed a year later. The Sahm rule fills that gap. Its design intent (articulated in Sahm's 2019 paper and subsequent congressional testimony) is to trigger automatic fiscal stabilisers (stimulus payments, extended unemployment insurance, fiscal transfers) as soon as labour-market deterioration begins, rather than after a confirmation lag of many months.

How the Calculation Works

The Sahm rule calculation has three steps, all using publicly available BLS unemployment data. First, take the three-month moving average of the headline US unemployment rate (the U-3 measure published monthly by the Bureau of Labor Statistics in the Current Population Survey). Second, find the lowest three-month average from any point in the prior twelve months, which functions as a rolling reference floor capturing the most recent cyclical low. Third, subtract the second number from the first. If the result is 0.50 percentage points or more, the rule has triggered.

A worked example using the April 2026 reading. The three-month moving average for February to April 2026 unemployment is approximately 4.07 percent. The lowest three-month average from any point in May 2025 through April 2026 was 3.60 percent (capturing the most recent local trough). The difference is 0.47 percentage points, the current reading. If the May 2026 number pushes the moving average above 4.10 percent (while the prior-12-month low remains 3.60 percent), the indicator will cross 0.50 and the rule will trigger.

The three-month moving average is used rather than a single month's reading because monthly unemployment data is noisy. Seasonal anomalies, weather events, single-firm layoff announcements, and other transient factors can produce significant month-over-month moves that do not represent a real change in labour-market conditions. The three-month smoothing reduces noise while preserving the timing sensitivity that real-time application requires. The rolling-12-month-low reference is used rather than a fixed historical floor because the rule needs to be applicable across different cyclical regimes; the floor adapts to whatever the recent labour-market low has been, so the rule operates symmetrically across business cycles.

The Historical Track Record

The Sahm rule has triggered before or coincident with every NBER-dated US recession since 1970. Specifically: late 1969 (the 1969-70 recession that NBER dated to December 1969); late 1973 (the 1973-75 recession dated to November 1973); early 1980 (the 1980 recession dated to January 1980); late 1981 (the 1981-82 recession dated to July 1981, with the rule triggering on the second cycle of the Volcker double-dip); mid-1990 (the 1990-91 recession dated to July 1990); early 2001 (the 2001 recession dated to March 2001); late 2007 (the Great Recession dated to December 2007); and early 2020 (the COVID recession dated to February 2020).

The rule has not produced a false positive in the post-1970 period in backtesting. Sahm tested various unemployment-rise thresholds against the NBER recession-dating record and found that 0.50 percentage points struck the optimal balance between sensitivity and specificity. A threshold of 0.30 would have produced multiple false signals (notably in 1986 and 1996). A threshold of 0.75 would have caught recessions too late to be useful as a real-time indicator. The 0.50 threshold has been validated against subsequent data since the rule's 2019 publication.

The 2020 COVID experience was a useful real-time test of the rule. The rule had not yet been formally adopted in policy circles when COVID hit, but applied to the COVID data, it triggered cleanly in March 2020, coincident with the NBER-subsequently-dated February 2020 recession peak. The COVID experience demonstrated that the rule could function during an unprecedented public-health shock as well as during conventional business-cycle downturns.

Why 0.50 Specifically

The 0.50 percentage-point threshold was derived empirically rather than theoretically. Sahm's 2019 paper systematically tested unemployment-rise thresholds from 0.10 to 1.00 in increments of 0.05 against the post-1948 NBER recession record. The 0.50 threshold maximised the area under the receiver-operating-characteristic curve, the standard statistical test for binary-classification rules. Lower thresholds caught recessions earlier but also produced false signals during labour-market noise periods. Higher thresholds avoided false signals but caught recessions too late to be useful for real-time policy responses.

The threshold is also approximately the level above which labour-market deterioration becomes self-reinforcing. Below 0.50, modest unemployment increases are typically reversed by subsequent labour-market dynamics (rehiring, new entrants, sector rotations). Above 0.50, the unemployment increase typically continues in a sustained way that translates to broader macroeconomic contraction. The 0.50 threshold thus captures both the empirical performance and a theoretical mechanism about labour-market dynamics.

The Live 2026 Reading

The April 2026 Sahm rule reading of 0.47 is the closest the indicator has come to the trigger threshold since the 2020 recession. The path to 0.47 has been gradual rather than sharp: the rule has risen from approximately 0.10 in early 2024 to 0.47 in April 2026 over twenty-six months. The drivers include the steady increase in the headline unemployment rate from the January 2023 trough of 3.4 percent to 4.1 percent as of April 2026, with the increase concentrated in 2024-25 (after the initial post-COVID labour-market overheating cooled).

Whether the indicator crosses 0.50 in 2026 depends on whether the unemployment rate continues to rise. The 0.50 trigger would be hit if the three-month average rises by approximately another 0.05 percentage points while the 12-month low remains at 3.60 percent. The 12-month low will roll forward as time passes, which means the trigger condition gets easier to satisfy as time passes if unemployment remains elevated even without further increases. A combination of stable elevated unemployment and the rolling-floor mechanic could trigger the rule by late 2026 even without further deterioration.

Claudia Sahm herself has expressed caution about applying her rule mechanically to the current period. In commentary through 2024-25, she has noted that post-COVID labour-market dynamics differ from earlier business cycles: the labour-force participation rate has been recovering rather than declining, immigration-driven labour-force expansion is contributing to measured unemployment in ways that do not reflect underlying labour-market weakness, and the relationship between unemployment and broader macroeconomic conditions may be different than in earlier cycles. Her caveat is that the rule's historical 0.50 crossing identified recessions reliably, but the post-COVID 0.50 crossing may not have the same meaning.

The Policy Significance

The Sahm rule's design intent was to trigger automatic fiscal stabilisers as soon as labour-market deterioration begins. The rule has been proposed (by Sahm and others, including in the Federal Reserve's policy-tools research and in academic discussions of fiscal-policy reform) as a trigger for stimulus payments, extended unemployment insurance, or fiscal-transfer programmes. The argument is that the political process of legislating recession-fighting fiscal stimulus is slow (months to years) and tends to operate too late in the business cycle to be maximally effective. A rule-triggered automatic response could deliver fiscal support during the recession itself, not after it has ended.

The 2020 CARES Act stimulus payments were not formally triggered by the Sahm rule (Congress passed them in response to the COVID shock directly), but the speed of the policy response (the first round of payments arrived within weeks of the unemployment spike) functionally resembled what a Sahm-rule-triggered automatic stabiliser would have produced. Subsequent policy discussions, including in the Council of Economic Advisers under the Biden administration and in academic fiscal-policy literature, have referenced Sahm rule mechanics as a model for recession-trigger design.

Whether the rule is ever formally adopted as an automatic fiscal-stabiliser trigger remains a political question. The technical case for it is strong; the political case requires accepting an automatic spending mechanism that bypasses congressional appropriations, which is constitutionally and politically challenging. As of 2026, the rule remains an informal real-time recession indicator rather than a formal policy trigger.

For the broader indicator framework, see the indicator dashboard. For other forward-looking indicators, see the yield curve indicator and the Conference Board LEI. For the 2020 recession application, see the COVID recession 2020.