What this site compares
Every coal shipment from Mongolia to China is counted twice: once by Mongolian customs as an export, and once by Chinese customs as an import. Statisticians call the pair mirror statistics. If coal left Mongolia without being declared, China’s import figures would be higher than Mongolia’s export figures for the same period.
The comparison uses coal and lignite (Harmonized System codes 2701 and 2702) on both sides. This matches Mongolia’s national “coal” statistic and the headline “coal and lignite” series that China’s customs publishes. UN Comtrade’s HS 2701 alone excludes lignite. In 2025, Mongolia sent China about 5.5 million tonnes of lignite, so comparing HS 2701 on one side with “coal and lignite” on the other would create a false gap of that size.
Where each number comes from
For every year and month, each side’s figure is taken from the best available source, in this order:
Mongolia (exports to China)
- A Mongolian customs bulletin entered by hand, when available.
- Mongolia’s own report to UN Comtrade, by partner country.
- Mongolia’s total coal exports to all countries from the National Statistics Office, multiplied by China’s share of those exports. This is used from 2024, because Mongolia has not yet reported those years to UN Comtrade. China’s share is taken from the latest year with a measured value (99.5% in 2023). The chart shows a range from the lowest share in the previous five years up to 100%. These years are marked approximate.
China (imports from Mongolia)
- A China customs release entered by hand from an official customs page.
- China’s own report to UN Comtrade.
- A China customs figure reported by an industry association or news agency, entered by hand with a link. These are marked approximate.
Tonnes and US dollars are chosen separately, so a year can have a comparable value in dollars even when its weight cannot be compared.
Years that cannot be compared
For 2016 and 2023, UN Comtrade did not receive China’s weight figures and filled in its own estimates. They are far too low: 12.2 million tonnes for 2016, against 25.3 million tonnes that Mongolia reported, and 43.2 million tonnes for 2023. This site never compares an estimated weight. For 2023, China’s figure of 70.0 million tonnes from a customs-based industry report is used instead and marked approximate. No reliable source has been found yet for 2016.
Why customs figures never match exactly
A gap between the two sides is expected and does not by itself indicate wrongdoing.
- Timing. Coal trucked across the border can wait in bonded yards at Ganqimaodu and other ports for days or weeks before Chinese customs clears it. A December export can be a January import.
- Valuation. Mongolia values exports free on board (FOB) at the border. China values imports including cost, insurance and freight (CIF). China’s value per tonne should be slightly higher.
- Weighing and moisture. Coal gains and loses water. Weighbridges on each side differ.
- Classification. The same coal can be declared under different codes, for example coking coal as other bituminous coal, or lignite as coal.
- Partner attribution. Coal declared for one destination can be recorded by China under a different origin, or pass through a third country.
- Revisions. Both countries revise their data. UN Comtrade’s figures change after publication. Every change is listed on the data page.
What this comparison cannot detect
Mirror statistics only reveal coal that was recorded on one side and not the other. They cannot reveal:
- coal that crossed the border without being recorded by either customs service;
- coal that was recorded correctly but sold below its value, which was central to several allegations about offtake contracts;
- coal misclassified within the coal and lignite group;
- theft or loss that happened before export, at the mine or in transport inside Mongolia.
A small customs gap therefore does not show that no coal was stolen. It shows whether the specific allegation “coal recorded in China but not in Mongolia” is supported by the published totals.
How the gap is calculated
- Gap = China’s figure minus Mongolia’s figure. Positive means China recorded more coal arriving than Mongolia recorded leaving.
- Gap % = the gap divided by Mongolia’s figure.
- Comparable: both figures come from customs data by partner country, or from an official customs release.
- Approximate: at least one figure is estimated from total exports, or comes from a news report citing customs.
- Totals over periods add up comparable years only (“comparable years only”), or comparable and approximate years (“including approximate years”). Excluded years are always listed. Adding each year’s difference regardless of direction is also shown, because different methods of summing produce very different totals.
When Mongolia’s own figures disagree
For 2021, Mongolia’s report to UN Comtrade says 19.6 million tonnes of coal and lignite were exported worldwide and 18.2 million tonnes to China. Mongolia’s National Statistics Office says 16.1 million tonnes in total. Within the UN Comtrade record for HS 2701, the net weight is 22% higher than the quantity reported in the same record. The year is flagged rather than hidden, and the comparison uses the UN Comtrade figure because it is specific to China.
Production and exports
Two Mongolian agencies publish coal production and exports. The National Statistics Office reports production from industry surveys and exports from customs. The Ministry of Mining’s regulator reports production, sales and exports in monthly PDF reports, which this site reads automatically. Their figures differ. In 2025 the regulator reported 78.4 million tonnes of exports, against 90.0 million tonnes recorded by customs.
Updates
The data is refreshed twice a month. Each update downloads every source again, rebuilds every figure and runs automated checks. A check that fails stops the update, and the previous version stays online. The results of every check are published below.