How the Cost of Living Index Is Calculated: Sources, Methodology, and Limitations
Transparency about data sources and methodology is essential for a reference site. This page explains exactly where our numbers come from, how the Cost of Living Index works, what it measures, what it misses, and the limitations you should keep in mind when using this data for important life decisions.
What Is the Cost of Living Index (COLI)?
The Cost of Living Index is produced by the Council for Community and Economic Research (C2ER), formerly known as ACCRA (American Chamber of Commerce Researchers Association). Founded in 1961, C2ER has published the COLI continuously since 1968, making it one of the longest-running price comparison datasets in the United States.
The index measures the relative price levels of consumer goods and services across participating urban areas. The national average is set to 100, providing an intuitive baseline: an area with an index of 85 means costs are 15% below the national average, while an area at 120 means costs are 20% above average.
C2ER collects data quarterly from over 300 participating urban areas across the United States. Trained researchers in each city gather prices for a standardized basket of goods and services, ensuring apples-to-apples comparisons. The data collection methodology is rigorously documented and audited to maintain consistency.
State-level indices, which are what we primarily present on this site, are calculated as population-weighted averages of the participating cities within each state. This means states with more participating cities have more robust averages, while states with fewer data points (particularly rural states) may be less precisely measured.
The Six Categories
The COLI measures prices across six major spending categories. Each category has its own sub-index, and the overall index is a weighted composite of all six.
Housing (Approx. 29% weight)
The largest component. Includes apartment rent (for a standard 2-bedroom unit), home purchase prices (for a specified home type), and mortgage rates. Housing is the primary driver of cost-of-living differences between states -- its sub-index ranges from 56 (Mississippi) to 319 (Hawaii), a far wider spread than any other category.
Groceries (Approx. 16% weight)
Prices for a standardized basket of grocery items including meat (ground beef, chicken breast), dairy (milk, eggs, cheese), produce (bananas, lettuce, tomatoes), bread, cereals, and other staples. Prices are collected from major grocery chains and independent grocers.
Utilities (Approx. 10% weight)
Monthly costs for electricity, natural gas, and telephone service. This category captures both rate differences (price per kWh) and usage differences (which vary by climate). States with extreme climates tend to have higher utility indices regardless of their electricity rates.
Transportation (Approx. 10% weight)
Includes gasoline prices, car maintenance (oil change, tire balancing), public transit where available, and auto insurance premiums. This category varies less between states than others, typically ranging from 90 to 136.
Healthcare (Approx. 4% weight)
Prices for a standard doctor visit, dentist visit, prescription medications, and hospital room rates. Note that this measures the price of services, not insurance premiums or total annual healthcare spending. The relatively low weight means healthcare costs have less influence on the overall COLI than their real-world importance might suggest.
Miscellaneous Goods and Services (Approx. 31% weight)
A broad category including clothing, personal care, restaurant meals, entertainment, and professional services. This is the second-largest component after housing and represents the wide range of consumer spending that doesn't fit into the other five categories.
What the COLI Does NOT Include
Understanding what is excluded from the COLI is as important as understanding what is included. These exclusions can significantly change the true cost comparison between states.
State and local taxes
This is the most impactful exclusion. The COLI does not include income tax, property tax, or sales tax. Texas (no income tax, 1.60% property tax) and Oregon (no sales tax, 9.9% income tax) would rank very differently if taxes were included. Our tax burden page fills this gap.
See our analysis →Savings rate / retirement contributions
The COLI measures spending, not savings capacity. A state where you can save 20% of your income provides more long-term financial security than one where you spend everything, even if the spending is at lower prices.
Quality of life
Crime rates, education quality, air quality, public infrastructure, cultural amenities, and access to nature are not measured. A state can be cheap precisely because it lacks investment in these areas.
Childcare costs
Childcare is one of the largest expenses for young families -- up to $24,000/year in expensive states. It is not included in the COLI despite being a major household expense.
Insurance costs
Auto insurance, homeowners insurance, and life insurance vary dramatically by state but are not captured in the index. Florida's property insurance crisis, for example, adds thousands to annual costs.
Climate comfort
The COLI captures utility costs but not the quality-of-life impact of climate. Six months of gray skies in the Pacific Northwest or extreme heat in Arizona affect daily life in ways that dollar figures cannot measure.
Our Data Sources
We compile data from multiple authoritative sources to provide the most comprehensive picture possible. Here is exactly what we use and when it was last updated.
| Data | Source | Last Updated |
|---|---|---|
| Cost of Living Index (overall + sub-indexes) | C2ER / COLI | Q1 2026 |
| Median home prices | Zillow Home Value Index | March 2026 |
| Average rent (2BR) | Zillow / Apartment List | March 2026 |
| Median household income | U.S. Census Bureau (ACS) | 2024 estimates |
| State tax rates (income, property, sales) | Tax Foundation | 2026 rates |
| Electricity rates and bills | U.S. Energy Information Administration | Q4 2025 |
| Healthcare costs and insurance | Kaiser Family Foundation | 2025 data |
| Uninsured rates | U.S. Census Bureau | 2024 estimates |
| Broadband data | FCC Broadband Deployment Report | 2025 |
| Grocery prices | USDA / BLS Consumer Price Index | Q1 2026 |
| Consumer expenditure patterns | BLS Consumer Expenditure Survey | 2024 |
Known Limitations and Caveats
No dataset is perfect. Here are the most important limitations of the data on this site.
State averages hide enormous city-level variation. New York state has a COLI of 126.5, but this averages Manhattan (~230), Brooklyn (~190), suburban Westchester (~150), and Buffalo (~90). Similarly, California at 142.2 includes San Francisco (~180), Los Angeles (~155), and Fresno (~105). If you are comparing specific cities, use metro-area data rather than state averages.
The COLI measures a fixed basket. If your spending pattern differs significantly from the average American, the index may not accurately represent your experience. Someone who spends 60% of income on housing (common in expensive cities) will experience more cost variation between states than someone who rents cheaply and spends heavily on travel.
Data has different freshness dates. Our COLI data is Q1 2026, but income data is from 2024 Census estimates. Home prices change monthly. We update all data quarterly and note the source date for each metric.
This is not financial advice. The data and analysis on this site are for informational purposes. Major life decisions like interstate relocation should involve consultation with financial advisors, tax professionals, and careful personal assessment of non-financial factors.
Frequently Asked Questions
What is the COLI?
The COLI (Cost of Living Index) is published by the Council for Community and Economic Research (C2ER). It measures relative price levels for consumer goods and services across participating urban areas in the United States. The national average is set to 100, so an index of 85 means costs are 15% below average and 120 means 20% above average.
How often is the COLI updated?
C2ER collects data quarterly from over 300 participating urban areas. Price data is gathered by trained researchers who visit local stores, housing markets, and service providers. State-level indices are calculated as population-weighted averages of the participating cities within each state.
What is NOT included in the COLI?
The standard COLI excludes: state and local taxes (income, property, sales), savings rates, quality of life measures (crime, education, climate), entertainment costs, and childcare costs. These exclusions are significant -- taxes alone can change the ranking of states dramatically. This site addresses the tax gap on our dedicated tax burden page.
Where does costoflivingbystate.com get its data?
We compile data from multiple authoritative sources: C2ER for the cost of living index, U.S. Census Bureau for income and demographic data, Bureau of Labor Statistics for consumer expenditure surveys, Energy Information Administration for utility data, Tax Foundation for tax rates, Kaiser Family Foundation for healthcare data, and Zillow/Apartment List for housing prices.
How accurate are state-level cost of living comparisons?
State-level indices are useful approximations but have inherent limitations. They average vastly different areas within a state -- New York state includes both Manhattan (estimated COLI 230+) and Buffalo (approximately 90). For the most accurate comparison, look at metro-area data. Our state indices are best used for initial screening and general comparison, not for budgeting to the dollar.