The performance metric is an indicator of how well a stake pool is performing. Considering that the slot leader election process is private, it is only possible to estimate how often the stake pool should be elected based on the number of actually produced blocks. A pool can be nominated more often than expected based on its stake.. For example, if a pool only produces half the number of blocks that it was nominated for, its performance rating is 50%. This could happen because the pool has a poor network connection, or has been turned off by its operator.
Performance ratings make more sense over a longer period of time. If a pool has not yet been selected to produce a block in the current epoch, its performance rating will be 0%, even if it is likely to produce blocks later in the epoch. Performance ratings of over 100% are possible if a pool creates more blocks than it was nominated to produce.
In Daedalus and Yoroi, performance contributes to a stake pool’s ranking.