NBER Business Cycle Dates

NBER Business Cycle Dates are the official peak and trough dates for U.S. business cycles, determined by the Business Cycle Dating Committee of the National Bureau of Economic Research (NBER). A peak marks the end of an expansion and the start of a contraction; a trough marks the end of a contraction and the start of an expansion. The data is free, public, and needs no API key. Used in, for example, Coimbra, Gomes, Michaelides & Shen, where NBER business cycle frequencies calibrate the recession/expansion Markov chain for the productivity shock process.

• Cost: free, public.
• API key: none required.
• Coverage: all U.S. business cycle turning points determined by the NBER committee. The earliest trough in the JSON is December 1854; the earliest peak is June 1857. The latest entry reflects the most recently dated cycle.
• Home: https://www.nber.org/research/business-cycle-dating

Access

The JSON endpoint returns an array of objects, each with a "peak" and a "trough" field as ISO date strings (e.g. {"peak":"1857-06-01","trough":"1858-12-01"}). The earliest entry has an empty peak and a trough of 1854-12-01, reflecting that the committee dates the first trough but not the preceding peak. Fetch directly, no authentication:

# No key required; returns a JSON array of peak/trough objects
curl -sL "https://data.nber.org/data/cycles/business_cycle_dates.json"

Note: the .csv variant of that path returns a 404. The JSON endpoint above is the confirmed no-key working path.

Load in Python

import pandas as pd

url = "https://data.nber.org/data/cycles/business_cycle_dates.json"
df = pd.read_json(url)

# Convert to datetime; replace empty strings with NaT
df["peak"]   = pd.to_datetime(df["peak"],   errors="coerce")
df["trough"] = pd.to_datetime(df["trough"], errors="coerce")

# Build a monthly recession indicator (1 = contraction, 0 = expansion)
# Expand each peak-trough pair across a monthly date range, then merge
# into a full calendar index.

Once peak and trough are datetime columns, you can expand each row across a monthly pd.date_range to build a 0/1 recession-indicator series aligned to any monthly panel dataset.

Gotchas (the ones that bite pipelines)

• Long announcement lag. The committee dates a turning point only after sufficient data accumulate, often several months to over a year after the event. The latest cycle in the JSON may be undated in real time. Do not treat the endpoint as a real-time or near-real-time signal.
• Day component is a convention, not a measurement. Peaks and troughs are identified to the month; the day is set to the first of the month by convention. Do not treat the day as meaningful. Work at monthly frequency or strip the day when converting to period labels.
• Monthly cycle dates are distinct from the NBER quarterly dates. The NBER also publishes quarterly turning points (used in some calibration contexts). They are not the same series. Confirm which frequency your source references.
• Determined by committee judgment, not a fixed rule. The NBER recession definition looks at depth, duration, and diffusion across indicators. It is not triggered by two consecutive quarters of negative GDP growth. Do not substitute one for the other in code or in writing.
• FRED USREC is a derived artifact. The FRED series USREC (and related USRECM, USRECD) is constructed from these dates but is a different object (monthly 0/1). If you use FRED, cite FRED and its construction note. If you use the NBER JSON, cite the NBER endpoint. Do not treat them as interchangeable in a citation.
• First entry has a missing peak. The array element for the 1854 trough has an empty string for "peak". Parse with errors="coerce" so it becomes NaT rather than raising.
• No versioning in the URL. The endpoint is updated in place when the committee issues new dates. Record the access date and the full array in your data snapshot so the pull is reproducible.

Reference

Field	Value
URL	https://data.nber.org/data/cycles/business_cycle_dates.json
Format	JSON array of {peak, trough} ISO date strings
Frequency	One row per business cycle
Earliest trough	December 1854
Earliest peak	June 1857
Update trigger	Committee announcement (irregular, long lag)
Key required	No

Citation

Cite the NBER, the Business Cycle Dating Committee, the retrieval URL, and the access date, for example: National Bureau of Economic Research, Business Cycle Dating Committee, “US Business Cycle Expansions and Contractions,” retrieved from https://data.nber.org/data/cycles/business_cycle_dates.json, accessed YYYY-MM-DD. Record the access date and archive the JSON array at time of download; the endpoint is updated in place with no version indicator.