The Block has reported on a decreased occurrence of stale blocks on the Bitcoin network. Stale blocks are invalid blocks which occur when miners continue to work on a block after it has been solved by another mining entity. It was noted that 63 stale blocks were observed in 2017. This decreased to six in 2018 and two year-to-date in 2019. Low-latency communication channels between major mining pools have been identified as the likely reason for the decrease.
Source: The Block