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There might never be a significant spike in bitcoin's mining hash rate. Such efforts have the potential to be cancelled out by shifts in bitcoin's difficulty mining algorithm, which could reduce the cost effectiveness of deploying a significant rise in hash power. The type of spike you're looking for could also suggest a significant spike in ASIC manufacturing quantities, which is unlikely.
That entire chart you posted
resembles a significant spike in btc mining power in my eyes. (Example: the spike above september 2018.)
Especially when factoring in decline of demand for nvidia GPUs and GPUs in general.
In June we had one of the biggest spikes in hashrat,e 14.88%, just two points below the ones in December
Ok, let's take it in another way....
Right now, an S9J at my current power rates is bringing me close to 60$.
At this profitability rate, people are still adding miners.
Back in January, the same ASIC would have earned you close to 6 times this!
Why wasn't there a bigger rise in difficulty, and why we have them right now, when it's clear profits are down, increases comparable to that of December and January ?
And no, it's not because of more efficient miners, the current generation is nowhere near an increase of that proportion in hashing efficiency. It's simply because there weren't enough miners.
A look at bitmain's thread will show you that they've hiked prices for miners by a factor of 2 and still got sold out in a matter of hours. Why? Because there was nothing else to mine with available for sale.GPU mining reached its peak pretty fast due to the insane rates at which they can manufacture video cards, that's all.
It's like a guy who has 10km2 of land and buys 5 tractors and another who buys them one by one as in his country there are no tractors for sale.
In the first case, the guy will reach it's maximum efficiency fast and doesn't need additional tractors, the other is slowly but surely getting there. The first manufacturer has seen a 500% increase in sales and now he must brace for a 400% drop, the other is maintaining its sales rates at the same number.
Simply put, Nvidia thought (?) ( I'm not sure they've forecasted a linear growth) that ETH would increase or at least maintain levels to 01-01-2018, which would reflect ina 3x reward for miners. But ...something went wrong