Hi, anyone could explain the following dataset drawn from UNcomtrade?  Is there anything wrong with the database?

No, there is nothing wrong with database. It is possible that country imports from itself (re-imports).

See http://comtrade.un.org/kb/article.aspx?id=10038

Thank you for your reply.

Then, I have two further questions on this:

1. Why this "imports-from-a country itself" only happens after around 2001? You may check the data, there is no such problem for early years.

2. I've noticed that your export data acturally includes "re-exports" as well, why there is no such problem for exports at all? (means there is no "export-to a country itself" at all in your database, for any product, any country, any year.)

 Thank you very much! Your help is really appreciated!

Best,

Anne

 1) It's due to "new" processing system introduced beginning of 2006. All data from year 2000 are planned to be reprocessed to take advantage of "new" system. This "new" system is able to identify re-import (but not the previous processing system)

2) Re-export has different concept with re-import. It is not "export to itself". Re-export happens if the country imports certain product and then, without changing the origin (of that product), the country exports them to other country. This means that re-export is export of commodity made/manufactured from other country. Hong Kong or Singapore or United Arab Emirates are considered have a large re-exports, as they act as a trading hub (do not make the products but simply import, may be done some minor processing such as packaging then export them again).