Methodology

The central problem with sauna import research is classification ambiguity. The method starts with that limitation rather than hiding it.

1. A category enters the tracker only with sauna evidence

We begin with U.S. Customs and Border Protection rulings involving an identifiable sauna product or component. A ruling establishes that a specific article, under the facts presented, was classified in a particular provision. Contrasting rulings are retained because differences in completeness, construction and use can change the result.

2. Official Census statistics are the trade source

The scheduled updater queries the U.S. Census Bureau International Trade API for the tracked 10-digit statistical reporting numbers. Beginning with this release, the updater is configured to retain the full available monthly series from January 2010 through the newest released month rather than only a rolling 36 months. Where the tariff schedule changed code structure, the series uses an explicit historical crosswalk rather than pretending the current code existed unchanged.

For prefabricated buildings of wood, the tracker uses historical provision 9406.00.4000 through December 2016 and 9406.10.0000 from January 2017 forward, reflecting the 2017 HTS restructuring. Each row can retain the source code used for that month.

3. Important values are rendered into static HTML

The JSON and CSV files remain canonical machine-readable outputs, but each successful update also regenerates the homepage, data tables, country rankings and monthly report. This prevents the published HTML from saying “awaiting sync” when the underlying dataset is already live and makes the main facts accessible without client-side JavaScript.

4. Broad categories are never added into a false sauna total

HTS 9406.10.0000 covers prefabricated buildings of wood, not only saunas. HTS 8516.29 covers electric space-heating apparatus beyond sauna heaters. HTS 8516.79 covers many domestic electrothermic appliances. Adding the category totals would produce an impressive-looking number that does not measure the U.S. sauna market.

Therefore: every series is labeled a “sauna-relevant tariff category.” Sauna Import does not publish a Census-derived total U.S. sauna import market size.

5. General imports vs. imports for consumption

The dataset retains both Census measures. General imports cover goods entering the U.S. customs territory. Imports for consumption cover goods entered for immediate consumption plus withdrawals from bonded warehouses for consumption. The appropriate measure depends on the research question.

6. Monthly origin-country data

For the newest available month, the updater retrieves country-of-origin values for every tracked category. Those rankings inherit the category's scope limitation; a country value for 9406.10 is not a sauna-only country value.

7. Immutable release snapshots

Each successful refresh writes a permanent snapshot under /data/archive/YYYY-MM/. That preserves the exact published dataset behind a dated report and prevents a long-lived citation from silently changing when the live dataset advances.

8. Failure behavior

If Census returns no released month, malformed JSON or otherwise unusable data, the updater stops instead of substituting invented values. Published stale data with a visible date are preferable to fabricated freshness.

9. What the dataset still cannot do

Broad HTS statistics cannot identify actual sauna shipments within the categories. Shipment-description or bill-of-lading data could improve product specificity, but only if a legally reusable and reproducible source is available.

Primary sources

See also the data dictionary, editorial policy and source library.