How We Research Costs
Last updated Oct 21, 2026
Every number on DollarMap has to pass the same four steps before it is published.
1. Find the best available source
We prefer, in order: U.S. government data (such as the Bureau of Labor Statistics, Census Bureau, IRS and Energy Information Administration), industry and trade associations, professional cost databases, and established cost publishers. Each source is listed at the end of the guide with its date.
2. Cross-check
Important figures are checked against at least two sources. When sources disagree, we say so and show both.
3. Show our own math
When we calculate something ourselves, such as cost per year of use, we label it as our calculation and explain the method next to the table.
4. Keep it fresh
Each guide shows the date it was last updated. We review guides at least once a year, and sooner when prices or rules change. Sources older than two years are used only as supporting evidence.
What we do not do
- We never invent numbers. A figure we cannot source does not get published.
- We do not accept payment to change a price, a ranking or a recommendation.
- Our guides are general information, not personal financial, legal or tax advice.
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