How we calculate
Exact formulas, the year-ago gap rule, and how the archive updates.
Where the numbers come from
Every figure on Finance Chicken comes from the U.S. Bureau of Labor Statistics, series APU0000708111: eggs, grade A, large, per dozen, U.S. city average, average price, not seasonally adjusted. The Bureau collects retail prices in grocery stores across U.S. cities and publishes one national average price per month. It is a national average, not what any single neighborhood shop charges.
The Bureau's data is public domain. Finance Chicken is not made by, affiliated with, or endorsed by the Bureau.
How changes are computed
Every percentage change uses the formula percent = (new / old - 1) x 100, computed from the full stored Bureau numbers before formatting. Dollar changes subtract the earlier price from the newer price. Every dollar figure is rounded to the nearest cent, with half a cent rounded up, and every percentage to one decimal place. Changes are computed from the exact stored prices, so a change can differ by one cent from the difference between the two rounded prices shown beside it.
On the home page, the year-over-year percentage is rounded once at display time to a whole number (half away from zero). On these archive pages, percentage changes are rounded to one decimal place for closer reading.
The year-ago rule and gap fallback
To compare the latest month with a year ago, our daily checking program looks first at the same month one year earlier. If that month has a published price, the comparison uses that figure.
If that month has no price published, the rule searches up to 2 months away in either direction, checking the earlier month first at each step: 1 month earlier, then 1 month later, then 2 months earlier, then 2 months later. The first month found with a price is used. If none of those five months has a price, no year-ago change is shown.
For example, October 2026 ($2.32) wants October 2025 for its year-ago reading. Since October 2025 has no published price, the fallback steps 1 month earlier to September 2025 ($3.49): (2.320 / 3.488 - 1) x 100 = -33.5% here, rounded to -33% on the home page.
Why a gap month has no price
In October 2025, the Bureau published no price for series APU0000708111. The archive stores that month as null and the tables print "no price published." In monthly tables and year summaries, neither a gap month nor the month after it shows a one-month change, and the chart shows a break in the line with a gap marker.
How these pages update
Each day a scheduled check reads the Bureau's public series. When a new monthly release arrives, the new month is added to the archive file in date order. Existing months may receive Bureau revisions, but no month is ever removed from the archive. All static pages and the sitemap are then rebuilt deterministically from the archive.
What this site does not do
Finance Chicken is a joke site built around one real price series. It provides general information only. It offers no buying guidance, no financial recommendations, no price projections, and no claims about why egg prices went up or down.