Whenever I see this graph, I wonder what’s supposed to represent. Total world investment in fusion, total world government spending, only US spending, or maybe only the part of the US Department of Energy earmarked for fusion research?
It probably is the last one, considering that the enacted 2012 budget of the US DOE for Fusion Energy Sciences was $401 MM ([1], p 16).
But then, why is only the US DOE supposed to invest in fusion?
In any case, as of 2020, this budget was increased to $671 MM [2].
That graph was for a crash program under the assumption that tokamaks work better than it turns out they do.
So, if that money had been allocated, it would have been a failure. There was also not the appreciation then of the grave nature of the engineering challenges facing fusion, even if the plasma physics worked wonderfully.
The implication that we'd have had fusion if that money had been spent is not supported by the evidence.
Yeap. This is the real answer. I guarantee you, if every government of the world came together and everyone said, "Okay, we're all going to pitch in 1% of GDP until we crack this thing," we'd have nuclear fusion in under 10 years.
Turns out doing cutting edge science is expensive... Jesus Christ, who knew?!