mining.thegenesisblock.com

We use the average monthly increase over the last 90 days. So a 77% increase per 30 day period compounded over 90 days (3 periods) gives a 457% increase. This was done to smooth out the spiking that occurs when the 30 day window changes between 2 and 3 difficulty periods, and to reduce the impact if there is a large spike in network speed in the near term that is not typical of the historical growth trend.