*Please note the axes are mislabeled. The left y-axis is 1/log difficulty and the right y-axis is log J/GH
People have been pondering whether cost of production matters in bitcoin value formation. And it certainly does:
http://papers.ssrn.com/abstract=2580904 But the rebuttal is well this may be the case now but it wasn't before. This post will try to give a reason why. And this is aside from the fact that there was rampant price manipulation and fraudulent trading in 2013 bringing the price well above $1,000 for no fundamental reason.
Economics would predict that marginal cost and marginal product, like supply and demand, will eventually converge to an equilibrium, and we see that during much of 2014 as ASIC tech kept pace with network growth in the graph above. But I am getting ahead of myself.
Whenever the orange line (energy efficiency) is above the blue line (difficulty), changes in difficulty are exceeding changes in efficiency and vice versa. So right now, difficulty is outpacing tech. progress. When ASIC first introduced, technology outpaced network growth (difficulty is a direct measure of network size)
So put one last way - the purple shaded area exists when the network growth is outpacing technological change. The data on GPU mining is admittedly not complete having just one representative data point, but I think that it nonetheless tells the same story.
Green areas exist when technological change is outpacing network growth. When they line up, the "supply and demand" is in equilibrium..
This also tells a nice economic story: In the beginning, people mined with CPUs and all was well. GPU mining came along and only served to crowd out CPU miners by growing the network exponentially. But since GPU cards are not developed with the express purpose of mining - they are made mainly for computer graphics - they were not induced to improve. GPUs just happened to be better than CPUs. It's like mining for gold with a shoe because it happens to be better than a sock. Also, since CPUs and GPUs run inside a PC which is normally left powered on anyhow, the electricity usage extracted for mining was less obvious than it is now. CPUs and GPUs also consume electricity to do other fun things like run spreadsheets and render video game worlds.
GPU mining also started to crowd out lesser GPUs. We see this as the difficulty chart starts to level out a bit in 2012.
This all changed with ASICs - specifically designed to mine. The shoe was replaced by a shovel. The shovel then turned into a steam shovel and then a modern-day mining operation. It is only with ASICs that the economics begin to line up because the induced technological change is making for better shovels and not finding something better than shoe which also not a shovel. It is easy to find a new low-cost producer of shovels by improving upon the last. Economic theory works when diggers use shovels and falls apart when they dig with shoes and socks. This is why shovels needed to be brought to bear for economic theory to show up in practice. Of course, this implies that Bitcoins are commodities produced in a competitive market, but that's fine by me!
Right now we are reaching a point where network growth is outpacing technological change, and the logical step will be for new 22 or 18nm technology to come online. Hashcoins Uranus is a machine that claims 0.26 J/GH efficiency but it might just be vaporware for now...