What Is the Impact of a High Pool-Switching Rate on the Effectiveness of the PPLNS System?

A high switching rate, often due to 'pool hopping,' reduces the effectiveness of PPLNS because miners join, submit shares, and then leave before a block is found, not contributing to the eventual payout. This leaves the remaining, dedicated miners to shoulder the work without the benefit of the short-term miners' shares, potentially lowering their effective return and increasing variance.