Methodology
Prices
Dollar prices come from the U.S. Bureau of Labor Statistics' Average Price series, a U.S. city average. Year-over-year inflation percentages come from the matching BLS Consumer Price Index series, not from the average-price series itself — BLS explicitly recommends against using average prices to measure change over time.
Some foods on this site don't yet have a confirmed BLS price series. Rather than estimate or guess, we mark those pages "estimate pending" and show no number until we've sourced one we trust.
Nutrition
Nutrition figures come from USDA FoodData Central, generally the SR Legacy dataset, which reports values per 100g of the raw or prepared food as specified on each page.
"Per dollar" metrics
Protein-per-dollar and calories-per-dollar are calculated by converting the BLS price (which is usually denominated per pound, dozen, or gallon) into a price per 100g, then dividing the USDA nutrient value by that price. We only calculate this when we have a real BLS price — never for estimated prices.
Sustainability tiers
Water-use and storage-life tiers are intentionally coarse (low / medium / high) rather than fake-precise numbers. They're drawn from published water-footprint research, primarily Mekonnen & Hoekstra's water footprint studies, cited on each food's page.
What we don't claim
We don't publish county- or city-level price data, because no federal source publishes food prices at that granularity. National and regional figures are genuinely more reliable than a confident-sounding local estimate would be.