The source, the translation, the year system and what the data leaves out.
All figures come from one page: the Tokyo Metropolitan Police Department's annual lost-property statistics, 遺失物取扱状況, last updated March 2, 2026. The tables there are HTML, not a data file, so the build script parses them directly and fails loudly if the expected tables are not present.
The prefecture directory comes from the National Police Agency's index of prefectural lost-property searches. All 47 are listed; 43 of them point at one shared national database and four run their own site.
Japanese government statistics use imperial era years. This data covers 令和7年, Reiwa 7, which is the calendar year 2025. The comparison column throughout is 令和6年, Reiwa 6, or 2024. Reiwa 1 was 2019.
Category and disposition names were translated by hand rather than machine, and the Japanese original is shown on the site next to every category so the mapping can be checked. The full table:
| Japanese | Used here |
|---|---|
| 証明書類 | Certificates and documents |
| 有価証券類 | Securities and vouchers |
| 衣類履物類 | Clothing and footwear |
| 電気製品類 | Electrical goods |
| 財布類 | Wallets and purses |
| かさ類 | Umbrellas |
| かばん類 | Bags |
| 携帯電話類 | Mobile phones |
| 貴金属類 | Jewellery and precious metals |
| カメラ眼鏡類 | Cameras and eyeglasses |
| 遺失者返還 | Returned to the owner |
| 拾得者引渡 | Given to the finder |
| 都帰属 | Became property of Tokyo |
| 廃棄・任意提出 | Discarded or surrendered |
The police publish two separate series and this site keeps them apart:
These are counts of different events and there is no key joining them. The "found versus reported lost" view puts them side by side to show an asymmetry; it is not a matching rate, and you cannot subtract one from the other to get a number of unreturned items. More cash is reported lost than is handed in, which is what you would expect and is not evidence of anything.
The disposition table is internally consistent: for each category, the four outcomes sum to that category's total. Return rates are computed straight from it. But that table's grand total, 4,750,389 items, differs slightly from the headline item count of 4,850,775, because the disposition table covers items processed in the year and the headline covers items received. Items received in late December are processed the following year. Do not mix the two.
build_japan.py in this repository fetches both pages and writes
data/data.json. It exits non-zero if the Tokyo page's table structure changes. The
police update the page once a year, in early March.
Built with AI assistance. Figures are parsed from the police tables rather than retyped, but the source page is the authority.