How a block of stone becomes a trade statistic

A block of marble leaves a quarry. Months later it is a line in a trade database. Between the two it passes through a customs form, a six-digit code and a national statistics office, and it is counted twice: once by the country that ships it and once by the country that receives it. The two numbers rarely match. This is how it works, step by step.

1. 01QuarryThe block ships with a customs declaration
2. 02CodeSix HS digits decide what it is
3. 03ReportThe country adds up every declaration
4. 04MirrorThe importer counts it too
5. 05ReconcileWe align, convert and document the gap
6. 06Data pointOne block, one line, one number

1. The block ships: a customs declaration

Before the block leaves the country, the exporter files a declaration: who exports, to which country, the net weight in kilograms, the value at the border, and a product code. Every trade figure starts as one of these lines.

2. It gets a code: six digits decide what it is

The Harmonized System (HS) gives the same code to the same product in every customs office in the world:

Raw stone sits in headings 2514 to 2516; worked stone (slabs, tiles, monuments, paving) in 6801 to 6803.

3. The country adds it up

Customs collects the declarations; the national statistics office adds up every one of them and publishes the country's trade figures, some months after the year ends. International databases such as UN Comtrade and Eurostat Comext gather those national figures.

4. The importer counts it too: mirror data

The same block is declared again on arrival. Statisticians call this mirror data, and the two records differ for mostly mechanical reasons:

• the exporter values it at departure (FOB), the importer with freight and insurance (CIF);
• the exporter records the month it left, the importer the month it arrived;
• each customs office makes its own reading of the code.

Two records of one shipment

FOB

Exporter: value at departure, month it left, its own reading of the code

CIF

Importer: value with freight and insurance, month it arrived, its own reading

Same block, two numbers, and usually both are right.

5. Reconciling before publishing

Before a figure reaches a KEYSTONE. dashboard it goes through the same checks every time: codes aligned across HS revisions, everything converted to the same units (USD and tonnes, or EUR for EU data), provisional years and missing reporters flagged, and both views kept with the gap documented. We don't replace the raw sources; we expose the seams between them.

6. One block, one line, one number

Added up with every other declaration, the block ends up in a single, comparable figure.

HS 2515.12 · marble and travertine, cut into blocks or slabs · 2024

• USD 1.06 bn

  world exports, value

• 4.8 Mt

  world exports, volume

In 2024 the world exported USD 1.06 billion of marble and travertine cut into blocks or slabs (HS 2515.12), 4.8 million tonnes. The World Stone Exports dashboard shows that figure by country and by year, at HS 4 or HS 6 detail. The full method is on our methodology page.