This section gives the background to the pricing data that have been collected and presented in this Guide.
Price sources: The two types of suppliers and buyers included in the Guide and how they differ
How prices were calculated: The exchange rates used to convert non-US dollar prices to US dollars and factors to consider when comparing costs
Nomenclature: How the list of products was selected and what names are used
Quality standards: Compliance with international quality standards
ATC/DDD system: The anatomical therapeutic chemical (ATC) and defined daily dose (DDD) methodologies for classification and measurement to assist in following and comparing trends in cost and use