According to the report, there are 875 identified urban areas in the world with 500,000 or more population as of 2013. Demographia released along with the report include a disclaimer that this list of data is compiled on best available information, the vary nature of which is changing rapidly and quality is improving as it becomes available, yet still remains highly variable between nations, and hefty revisions are not unforeseen for the future. Appropriate caution is therefore advised.