One has to consider the opportunity costs of not investing or paying down debt as well, but the safer route is also the route with less variance and more security. (investitwisely.com)
There is much less variance today than say in the 1960s, but perfect consistency is hard, especially once the vehicles have left the factory and been driven and maintained by different people. (mechanics.stackexchange.com)
Repeat for a solar index of your choice and the original record is much cleaner e.g. has a lot less variance. (realclimate.org)