The number of transactions included in the blockchain each day
Daily Transaction count is one of the most important and controversial metrics for the Bitcoin Cash (BCH) network. A key driver of the Bitcoin Cash (BCH) fork and the Segwit (BTC) fork was a dispute over the importance of enabling low-fee on-chain transactions (the type measured by this chart). Today, this fee is low for Bitcoin Cash (BCH) (about 1 satoshi per byte, or less than USD $0.01), but high and unpredictable for Bitcoin Core (BTC) (anywhere from 20 satoshis per byte to over 1,000 satoshi per byte, between 10 cents and dozens of dollars depending on transaction volume).
Because all confirmed transactions pay a fee, each confirmed transaction represents someone's desire to send a Bitcoin Cash (BCH) transaction instead of any alternative use of that cost. Bitcoin Cash (BCH) transactions can be executed and automated by software, but this is limited by the bandwidth of the network and required fees. Occasionally large numbers of transactions will be made in a short time interval, leading to long confirmation times and some transactions that may not confirm at all. While some attribute unusually high transaction volume to "spam" transactions, others hold that any transactions following the rules of the network are valid.
Because transactions have a real world cost, daily transaction count is one of the best ways to model growth in users of the Bitcoin Cash (BCH) network. Daily transaction count could be manipulated in the short term, but it's difficult to identify plausible motives given the high costs (while Bitcoin Cash (BCH) transactions are individually low fee, it would be expensive for any single entity to create blocks full of low-fee BCH transactions).