The mistake might be on my part, but I think where this may be going wrong is I assume the cost needs to be repeated each year (i.e. you spent 1B to reduce risk by 1% in 2018, then have to spend another 1B to reduce risk by 1% in 2019). So if you assume a single 1B pulse reduces x risk across the century by 1%, then you do get 100 fold better results.
I mainly chose the device of some costly ‘project X’ as it is hard to get a handle on (e.g.) whether 10^-10 reduction in xrisk/​$ is a plausible figure or not. Given this, I might see if I can tweak the wording to make it clearer—or at least make any mistake I am making easier to diagnose.
The mistake might be on my part, but I think where this may be going wrong is I assume the cost needs to be repeated each year (i.e. you spent 1B to reduce risk by 1% in 2018, then have to spend another 1B to reduce risk by 1% in 2019). So if you assume a single 1B pulse reduces x risk across the century by 1%, then you do get 100 fold better results.
I mainly chose the device of some costly ‘project X’ as it is hard to get a handle on (e.g.) whether 10^-10 reduction in xrisk/​$ is a plausible figure or not. Given this, I might see if I can tweak the wording to make it clearer—or at least make any mistake I am making easier to diagnose.
Ah sorry yes you are right—I had misread the cost as £1 Billion total, not £1 Billion per year!