Bitcoin Forum

Even if net GH/MH's decreases.

For example net rate was .5 GH now .3-4

Network Info
Difficulty    5.25251222
Est Next Difficulty    6.61213182 (Change in 11 Blocks)
Est. Avg. Time per Block    63.55 seconds
Current Block    20689

Shouldn't a decrease in hashrate result in a decrease in difficulty?

Difficulty usually uses a formula which averages hashrate since the last difficulty change. If a coin adjusts difficulty every two weeks and network hashrate was 2GH/s for 1 week, then .5GH/s for the next week, you'll end up with a difficulty reflecting a 1.25GH/s hashrate. In some cases, this averaging can lead to "difficulty death spirals" if miners pump and dump, where difficulty is too high for the network, leading to extremely long confirmation times, which leads to a lot of people abandoning the coin, which causes even more hashpower to leave the network until you can't get a block confirmed.

Because of the "difficulty death spiral" and some other reasons, a particular coin's difficulty may have other mechanics at play than what I went over. (for example, Bitcoin has a floor and ceiling on maximum % deviation from previous difficulty... I think it's 20%, maybe 40%. If hashpower quadruples for a couple weeks on Bitcoin network, difficulty will only rise 20%, not 400%. If hashpower then disappears and we're left with the original hashpower, blocks would take only two minutes over the target confirmation time, rather than 30 minutes extra)

these are the predicted difficulties and not the actual next block's difficulty.