Open three different cost-of-living comparison sites and you'll get three different answers for the same city pair. The math isn't wrong — the inputs are.
Where the standard index comes from
The most-cited U.S. index, C2ER, samples about 60 priced items across 300+ cities every quarter. The basket dates back to the 1980s and still weights groceries near 13% — about double their actual share of modern household spending.
What the index gets right
- Relative prices for tradable goods (groceries, household items)
- Healthcare premium variation across regions
- Utility costs adjusted for climate
What it gets wrong
- Housing is sampled from a narrow set of mid-tier rentals and homes, missing both the cheap and expensive ends
- Transportation assumes car ownership — useless for dense, transit-friendly cities
- Childcare, the single largest variable expense for many families, is excluded entirely
- State and local taxes are not part of the standard index
The better way to compare
Rather than trusting a composite, build your own quick index from four numbers you can pull in under 15 minutes per city:
- 01Median rent for the bedroom count you need (Zillow / Apartments.com)
- 02Annual property tax on a median home (county assessor)
- 03State + local income tax effective rate at your bracket (Tax Foundation)
- 04Average commute cost: monthly transit pass OR (miles × 2 × workdays × $0.55)
How Nabelly builds its numbers
We publish source-attributed values for housing (Zillow / Redfin), groceries (BLS CPI by metro), healthcare (HHS MEPS), and taxes (state revenue departments), and recompute monthly. We do not publish a single composite index — you'll always see the underlying numbers.
Questions readers ask
Q01Is BLS data better than C2ER?
For temporal comparisons within one city, yes. For cross-city comparison at a point in time, C2ER and similar surveys are still the standard, with the caveats above.
Q02Should I trust salary-comparison calculators?
Treat them as a starting point. Most use the same flawed indexes. Verify with concrete rent + tax numbers for the specific neighborhoods you'd consider.
Q03Why is my real cost so different from the index prediction?
Usually housing. Indexes assume you'll pay near median. If you trade up or down on housing, your effective cost shifts 10–20% from the index estimate.
