Because of the limitations of the difficulty retarget. The limitation being that it can only adjust the difficulty based on how long the previous blocks were found. No blocks found, no difficulty adjustment because the difficulty of the next block can't be changed once it's set in the previous block. So if a block is not found for lack of miners or just due to bad luck, the difficulty retarget will overcompensates and reduces the difficulty so much so that the next few blocks will be mined faster then the difficutly retarget overshoots again but this time it increases the difficulty too much. And so on and on.
The super fast speed of ASIC miners augment this problem.
This is why a few coins added multiple parallel algos (Joincoin, Digibyte, Myriad, etc) which allows the difficulty retarget to change the difficulty of an algo without having to find a block doing that algo.
Topic: Why does the profitability of mining dash fluctuate so much? (Read 522 times)
I have been checking the profitability calculators for dash several times a day and throughout the day the profit varies by thousands of dollars annually, why does this vary so much?
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