Hash-rate: the hash-rate of the Bitcoin network is the aggregate work put into the system by all the miners and hence is a representation of the network’s security. With the probabilistic finality of Bitcoin, any set of actors with 51% of the hash-rate can create the longest chain around which consensus forms: a higher hash-rate implies a higher difficulty to attack the network.

Number of miners controlling 51% of hash-rate: indicating the degree of centralisation of the network around certain miners & mining pools. The lower the number, the higher the risk of collusion for an attack on the network.

Number of transactions: can be used to represent the usage of the network as a means of exchange, but not to adequately represent the usage of the network as a store of value. Can be gamed by a set of bots spamming a high number of low value transactions, and can be a misrepresentation as one transaction can encode many transfers via batching or sidechains / Lightning Network.

Aggregate transaction value: the aggregate value of all transactions within a certain time period, showing the value transferred over the network.

Total market capitalisation: as a store of value, the total market capitalisation of Bitcoin matters as a representation of the amount of value it is entrusted with (with a caveat that some Bitcoins are lost or dormant).

Block rewards available to miners: main source of revenue for the miners securing the network. The block reward multiplied by the price of Bitcoin represent the value available in exchange for hash-power.

Transaction fees paid to miners: source of revenue for miners that should increase in importance as the block rewards continue halving. Expected to become the primary source of revenues for miners securing the network in the coming decades.