Background: A lot of scientists have tried to shed light on dark web markets. They did this by scraping these marketplaces over a period of time and describe what they were seeing. However, the methods used to measure these markets were never validated before. Research goal: This research will identify and validate the methods that are used in the literature to measure darknet marketplaces. Methods: To validate these methods, a novel dataset is used, namely the confiscated backend of a market. This dataset is cleaned and used to analyze the accuracy of these proxies on. Results: It is found that the number of transactions, revenue, and market share can be estimated with a high amount of explained variance. The predictions are precise enough to find prominent vendors on the market. The designed method of calculating the illegally obtained profits of a darknet vendor is easy to understand and could be used by law enforcement agencies. Finally, it is found that some vendors register to a market early as a strategy to ensure their business continuity.