Bureau of Labor Statistics (BLS)

The Bureau of Labor Statistics (BLS) publishes U.S. labor-force, employment, wage, and price statistics: the labor-force participation rate, the unemployment rate, payroll employment, the Consumer Price Index (CPI) and Producer Price Index (PPI), job openings (JOLTS), and county-by-industry employment and wages (the Quarterly Census of Employment and Wages, QCEW). The public data API and the QCEW files are free and need no key. Used in, for example, Beyhaghi, Fracassi & Weitzner for county-level and financial-industry wages, and the CPI-U series underlies Dittmar, Hsu, Roussellet & Simasek as the inflation measure (obtained there through FRED, which re-publishes BLS series).

• Cost: free, public.
• API key: none required. The public API v2 works with no key at lower limits (25 queries/day, up to 10 years, up to 25 series per call). A free BLS_API_KEY raises the limits (500 queries/day, 20 years, 50 series).
• Coverage: national labor-force and price series (monthly, from the mid-twentieth century for the headline series); QCEW county-by-industry employment and wages (quarterly, from 1990).
• Home: https://www.bls.gov/data/ · API: https://api.bls.gov/publicAPI/v2/timeseries/data/ · QCEW: https://www.bls.gov/cew/

Access

Time series via the public API (no key)

The API takes a JSON POST with a list of series IDs and a year range. No key is needed for low-volume use:

# Unemployment rate (LNS14000000), 2023-2024, no key
curl -s -X POST "https://api.bls.gov/publicAPI/v2/timeseries/data/" \
  -H "Content-Type: application/json" \
  -d '{"seriesid":["LNS14000000"],"startyear":"2023","endyear":"2024"}'

Add "registrationkey":"<BLS_API_KEY>" to the JSON body to use a free key and the higher limits.

import requests

def bls_series(series_ids, start, end, key=None):
    body = {"seriesid": list(series_ids), "startyear": str(start),
            "endyear": str(end)}
    if key:
        body["registrationkey"] = key
    r = requests.post(
        "https://api.bls.gov/publicAPI/v2/timeseries/data/", json=body)
    r.raise_for_status()
    out = r.json()
    assert out["status"] == "REQUEST_SUCCEEDED", out.get("message")
    return out["Results"]["series"]   # each: seriesID + data[] (year, period, value)

QCEW county wages (no key)

County-by-industry employment and wages come as direct CSV downloads keyed by the 5-digit area FIPS code. No key, no API body:

# Los Angeles County (06037), 2022 Q1, all industries: establishments,
# employment, and wages by industry/ownership
curl -s -o qcew_06037_2022q1.csv \
  "https://data.bls.gov/cew/data/api/2022/1/area/06037.csv"

The header row names the fields (area_fips, own_code, industry_code, qtrly_estabs, employment columns, total_qtrly_wages, avg_wkly_wage, and a disclosure_code flag).

Flat files

The full published tables, including discontinued and detailed series, live as flat files under https://download.bls.gov/pub/time.series/, organized by survey prefix (for example ln/ for the CPS labor-force series, cu/ for CPI-U). These need no key.

Gotchas (the ones that bite pipelines)

• The seasonal-adjustment flag is hidden in the series ID. For the CPS labor series the third letter sets it: LNS... is seasonally adjusted, LNU... is not. They are the same concept with different numbers. The same split holds across surveys (CES/CEU, CUUR/CUSR, WPU/WPS). Pick one deliberately and state which you used.
• The no-key tier is rate-limited. Without a key you get 25 queries per day, 10 years, and 25 series per call. A batch backfill will hit that wall; either register a free key or cache aggressively. Closed-period data is immutable, so cache hits are safe.
• Series are revised. Monthly CES employment and CPI figures are revised (CES has preliminary, second, and final estimates, plus annual benchmark revisions). Pin the vintage you pulled; a re-pull of a recent month can change the number.
• QCEW cells are suppressed for confidentiality. A non-empty disclosure_code marks a cell withheld to protect an identifiable employer, so employment and wage figures are blanked there. A blank is not a zero; handle the disclosure flag.
• QCEW counts jobs and wages, not firm financials. It is administrative unemployment-insurance data covering covered employment by establishment location and industry, not a firm-level financial panel.
• The API is the same series FRED re-publishes, not a different number. FRED mirrors many headline BLS series (for example seasonally adjusted CPI-U CUSR0000SA0 as CPIAUCSL; the not-seasonally-adjusted CUUR0000SA0 maps to CPIAUCNS instead). Cite the source you actually pulled from; do not imply two independent measurements.

Series-ID prefixes

Prefix	Survey	Common use
LNS / LNU	CPS (household), SA / NSA	LFPR, employment-population ratio, unemployment
CES / CEU	CES (establishment), SA / NSA	Payroll employment, hours, earnings
CUUR / CUSR	CPI-U, NSA / SA	Consumer prices
WPU / WPS	PPI, NSA / SA	Producer prices
JTU	JOLTS	Job openings, hires, quits, layoffs
ENU	QCEW	County by industry employment and wages
SMU / SMS	State and area CES, NSA / SA	Sub-national payrolls

Discover exact series IDs with the BLS data finder (https://www.bls.gov/data/) or the per-survey “Series ID formats” pages.

Citation

Cite the U.S. Bureau of Labor Statistics, the survey and series IDs used (with the seasonal-adjustment choice), the period range, the retrieval URL, and the access date. For QCEW, record the area FIPS, year, quarter, and ownership and industry codes so the pull is reproducible.