How do international organizations like IMF, WB, and CIA Fact Book collect statistics regarding a country's economic indicators?
What is their primary source of information?
How do international organizations like IMF, WB, and CIA Fact Book collect statistics regarding a country's economic indicators?
What is their primary source of information?
I don't know how CIA gets its information from other countries on their economic performance, but I can tell you that IMF and WB have residence representative offices in member countries. Central Banks, various ministries and other government agencies supply periodic performance records to these offices.
Building on london's answer, and the question in the comments about how agencies deal with erroneous data supplied by governments, here is a relevant IMF paper.
"How to Check Integrity of Fiscal Data". The abstract:
The accuracy and reliability of government accounts and fiscal data is an issue in a number of countries, with significant and persistent discrepancies that can indicate underlying weaknesses in the country’s public financial management system. This note provides guidance on how to detect issues with data quality, perform integrity checks, and reconcile fiscal data from various sources. It discusses the importance of reconciliation to provide reasonable assurance on the quality and reliability of government fiscal data, explores the main reasons for which discrepancies may arise, and explains how to conduct quality checks. The note concludes with recommendations for country teams of concrete steps to ensure data quality.
In short, the IMF advocates a process of reconciliation, whereby supplied data is checked for consistence with additional sources. For example, as london noted in a comment, any time a government claims to have paid a supplier, that transaction should also show up in the accounts of the supplier.