Statistical surveys
Contents
The American Community Survey (ACS) is the largest continuous household survey in the United States and is a primary source of detailed demographic, social, and economic data.
It is critical to understand that the ACS provides estimates based on a sample, not exact counts like the Decennial Census. This is reflected in the requirement to report a Margin of Error (MOE) for all estimates.
1. ACS Sample Size
The ACS is an ongoing survey, with addresses selected every month throughout the year.
| • | Targeted Annual Sample Size: The ACS currently targets approximately 3.5 million housing unit addresses annually across the 50 states and the District of Columbia. An additional 36,000 addresses are sampled for the Puerto Rico Community Survey (PRCS). |
| • | Sampling Rate: The overall sample represents about 1 in 40 housing units annually. This is a much smaller proportion than the 1-in-6 sample used by the old Decennial Census "long form" that the ACS replaced. |
| • | Geographic Sampling: Sampling rates are assigned at the census block level and are generally higher in less-populous areas to ensure sufficient data precision for small counties and places. |
| • | Group Quarters (GQs): Approximately 2.5% of the population living in Group Quarters (like nursing homes, prisons, and dormitories) are also sampled annually. |
2. Key Sample Characteristics
The ACS collects data on a broad range of subjects, which are often grouped into four major characteristic types:
A. Demographic Characteristics
| • | Age and Sex: Detailed single-year-of-age data. |
| • | Race and Hispanic or Latino Origin: Counts and distributions. |
| • | Relationship: Household and family relationships (e.g., householder, spouse, child). |
| • | Household Type: Family versus non-family households. |
| • | Migration/Residence 1 Year Ago: Used to track internal migration. |
| • | Citizenship Status and Place of Birth. |
B. Social Characteristics
| • | Educational Attainment: High school diploma, college degree, etc. |
| • | School Enrollment: Public vs. private, level of schooling. |
| • | Marital Status and Marital History (since 2008). |
| • | Veteran Status and Period of Military Service. |
| • | Disability Status. |
| • | Language Spoken at Home and English Language Proficiency. |
C. Economic Characteristics
| • | Income and Earnings: Household, family, and individual income in the past 12 months. |
| • | Employment Status: Labor force participation, unemployment. |
| • | Industry and Occupation. |
| • | Commuting (Journey to Work): Means of transportation, travel time. |
| • | Health Insurance Coverage. |
| • | Poverty Status. |
D. Housing Characteristics
| • | Housing Unit Type and Occupancy. |
| • | Tenure: Owner-occupied vs. Renter-occupied. |
| • | Value of Home or Monthly Rent/Owner Costs. |
| • | Year Built, Number of Rooms/Bedrooms, and Plumbing Facilities. |
3. Data Products and Reliability (Period Estimates)
Because the ACS collects data continuously, its estimates represent period estimates—the average characteristics over the collection time—rather than a single "point-in-time" snapshot.
Estimate Type |
Data Collection Period |
Minimum Population Threshold |
Focus |
1-Year Estimates |
12 months |
65,000+ |
Most current data, but least reliable (largest MOE). Good for large, changing areas. |
5-Year Estimates |
60 months |
All areas (down to Census Block Group) |
Most reliable (smallest MOE), but least current. Essential for small geographies. |