system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: When people say that a specific industry is valued at whatever they say it's valued at, how do they know that? Ex: "The global coffee industry is valued at $450 Billion"
gpt
It depends. For some items, they can use retail sales records, or import/export trade documents, or industry/trade associations. These are almost always estimates - data collected from various sources then put in some model to get a number. They're mostly a rough guide.