When Numbers Diverge:
A Tale of Two Trading Partners
Building Harvard Growth Lab's International Trade Datasets
By Sebastián Bustos, Ellie Jackson, David Torun, Brendan Leonard, Nil Tuzcu, Piotr Lukaszuk, Annie White, Ricardo Hausmann & Muhammed A. Yıldırım
Trade data powers decisions, from public policy to private investment. But the raw numbers often don't add up. When two countries trade, both report the same transaction, yet their figures often disagree. And over time, product classifications change, making it hard to compare trade data between countries. Here we explain how the Harvard Growth Lab builds a cleaner, more consistent trade dataset by: 1) Reconciling discrepancies between exporters and importers (mirroring); 2) Harmonizing product categories across classification changes using economically relevant weights. The end result is a publicly available trade dataset and a resource for researchers, policymakers, and anyone curious about how the world trades.
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Reporting Country
Reporting Country
$497M more
Country A and Country B are trading partners. In theory, their reported trade data should align. In practice, it rarely does.
This discrepancy highlights two persistent challenges in international trade data: (1) how countries report trade, and (2) how products are mapped across classification systems. This site explains both issues, and how the Growth Lab handles them.
1. The Reporting Problem
In 2024, both Country A and Country B submitted their bilateral trade statistics to UN Comtrade for the calendar year 2023. Despite their shared transactions, their reported trades with each other did not align.
For example, Country A reported that they exported $603 million to Country B.
Meanwhile, Country B reported that they imported $1.1 billion from Country A.
Both countries are reporting the same flow of goods. Yet Country A reported $497 million less than Country B.
If Country B reports imports 82% higher than Country A reports exports, what is the true value of trade transacted between the two countries?
Now, scale this example of Country A and Country B to all countries and their trading partners. The discrepancies compound.