CoinMetrics with a post on how reliable crypto data may be among various sources. Despite access to a lot of raw data, there’s a lot of issues with interpreting that data. It’s part of the ongoing problem of figuring out how to value cryptoassets:
So to conclude, on-chain volume and transaction count can both be faked and can be tricky to estimate. Exchange volume must be viewed fairly skeptically. Market cap has a whole host of methodological issues. Generated coins and fees, however, are much more concrete.
via On data and certainty at Coin Metrics