U.S. Census Bureau public data

U.S. Census Bureau public data covers a family of distinct statistical products used in finance and economics research: Business Dynamics Statistics (BDS: firm and establishment counts, entry and exit, job creation and destruction, by age and size), Quarterly Workforce Indicators (QWI: local employment and earnings flows), the American Community Survey (ACS: demographic and economic characteristics down to ZIP code and census tract), County Business Patterns (CBP: establishment counts and payroll by industry and county), and official population estimates. These products are cited in, for example, Barkai & Panageas for Business Dynamics Statistics (young-firm employment share, firm-size distribution, job creation and destruction), and Beyhaghi, Fracassi & Weitzner for county-level population estimates.

• Cost: free, no paywall.
• API key: free key required for the api.census.gov API (returns “Missing Key” otherwise); the bulk flat files on www2.census.gov need no key.
• Coverage: U.S. firms, establishments, employment flows, demographics, and population, from the 1970s onward depending on the product.
• Home: https://www.census.gov/data.html · API docs: https://www.census.gov/data/developers.html

Access

Option 1: No-key bulk flat files (verified path)

The BDS time-series CSVs are published as flat files on www2.census.gov and need no authentication. The 2022 release is at:

https://www2.census.gov/programs-surveys/bds/tables/time-series/2022/bds2022.csv

Key columns: year, firms, estabs, emp, estabs_entry, estabs_exit, job_creation, job_destruction, job_creation_rate, job_destruction_rate.

import pandas as pd

bds = pd.read_csv(
    "https://www2.census.gov/programs-surveys/bds/tables/time-series/2022/bds2022.csv",
    dtype=str,   # suppress int-parsing of suppressed cells marked "S"
)
# Convert numeric columns explicitly after handling suppression flags
numeric_cols = ["year", "firms", "estabs", "emp",
                "estabs_entry", "estabs_exit",
                "job_creation", "job_destruction"]
bds[numeric_cols] = bds[numeric_cols].apply(pd.to_numeric, errors="coerce")

This path is the genuinely no-key route and is what the verified stamp above covers. Analogous bulk files exist for CBP and population estimates under www2.census.gov/programs-surveys/.

Option 2: api.census.gov (key required)

Get a free key at https://www.census.gov/data/developers.html and store it in your environment (e.g. CENSUS_API_KEY=...); never hard-code it.

Example: ACS 5-year estimates for median household income (B19013_001E) by county in California:

import os, requests, pandas as pd

key = os.environ["CENSUS_API_KEY"]
url = (
    "https://api.census.gov/data/2022/acs/acs5"
    "?get=NAME,B19013_001E"
    "&for=county:*"
    "&in=state:06"
    f"&key={key}"
)
data = requests.get(url).json()
df = pd.DataFrame(data[1:], columns=data[0])
df["B19013_001E"] = pd.to_numeric(df["B19013_001E"], errors="coerce")

The API supports BDS, ACS, CBP, QWI, and population estimates with consistent ?get=<variables>&for=<geography>&key=<key> syntax. Variable and geography codes are listed in the API discovery endpoint at https://api.census.gov/data/2022/acs/acs5/variables.json.

Gotchas (the ones that bite pipelines)

• The API requires a free key; the bulk files do not. The api.census.gov endpoint returns a plain-text “Missing Key” error (not a JSON error object) when called without a key. The genuinely no-key path is the bulk flat files on www2.census.gov as shown in Option 1 above.
• “Census data” is not one dataset. BDS, QWI, ACS, CBP, and population estimates have different geographies, frequencies, disclosure rules, and update cadences. Code that treats them interchangeably will silently produce nonsense. Pick the specific product and vintage for each research use, and document it.
• Disclosure avoidance and noise injection. The post-2020 differential privacy regime changed how small-cell counts are released. Suppressed cells appear as "S" or "D" in bulk files, and noise-injected counts in small geographies can be negative or implausibly volatile. This regime is a break from earlier products and affects panel comparability.
• ACS margins of error must be propagated. Every ACS estimate ships with a margin-of-error column (suffix MA or M). Ignoring it and treating point estimates as exact is incorrect, especially for small geographies or small subgroups. Also: 1-year ACS (larger geographies, current) and 5-year ACS (smaller geographies, averaged) are different products and must not be mixed in a panel without adjustment.
• NAICS and geography vintages change. Industry codes are revised across NAICS releases (1997, 2002, 2007, 2012, 2017, 2022), and county FIPS codes change when counties are created, dissolved, or renamed. Concatenating CBP or BDS panels across NAICS transitions or county changes requires crosswalks, which the Census provides but which must be applied explicitly.
• BDS and QWI measure jobs and establishments, not firm financials. These products describe entry, exit, employment flows, and earnings, not revenue, assets, or profitability. They complement Compustat or CRSP for macro-finance calibration but do not substitute for firm-level financial data.

Products at a glance

Product	Unit	Geography	Frequency	Key use in finance research
BDS	Firm / establishment	Nation, state, metro, county	Annual	Entry/exit rates, firm-age distribution, job flows
QWI	Worker / establishment	State, metro, county, WIA	Quarterly	Local labor market dynamics, earnings by firm age
ACS	Household / person	Nation down to tract/ZIP (5-yr)	Annual	Demographics, income, education for local-area work
CBP	Establishment	Nation, state, county, ZIP	Annual	Industry structure, payroll, establishment counts
Population estimates	Person	Nation, state, county	Annual	County-level controls, normalization denominators

Citation

Cite the specific Census product and vintage, not just “Census.” Examples:

• U.S. Census Bureau, Business Dynamics Statistics, 2022 release, https://www.census.gov/programs-surveys/bds.html, accessed YYYY-MM-DD.
• U.S. Census Bureau, American Community Survey 5-Year Estimates, 2022, Table B19013, accessed via api.census.gov, accessed YYYY-MM-DD.
• U.S. Census Bureau, County Business Patterns, 2021, https://www.census.gov/programs-surveys/cbp.html, accessed YYYY-MM-DD.

Each product’s landing page lists the suggested citation format and the appropriate technical documentation to reference.