> there's already a term for what you are referring to
A bubble suggests the inherent overvaluation in a natural market cycle. Inflation is used intentionally to differentiate that the price is higher because money was artificially injected, so the normal rules for identifying market exuberance (assuming you had perfect information) are distorted.
> That is the job of legislators, not central banks.
The central banks buy whatever debt the legislators need to be financed, in the real world. During the pandemic, that meant buying insanely expensive (low interest) treasuries to finance stimulus checks, as well as direct economic injections.
> The price of copper tripled between December 2008 and February 2011:
That's one commodity. Indexes exist so that we may prevent this misleading thinking. Law of large numbers, etc.
As I posted a few weeks ago, random length lumber futures are up 200% since the pandemic began. Copper and soybean futures are both up 60%. Industrial steel is up 133%. Industrial silicon is up 70%. Sunflower oil +114%. Wheat +20%. Platinum +29%. Gold +20%. Aluminum +32%. Energy futures +30%. Natural gas +42%.
The real estate market is in a frenzy. SPX is up 25%, despite almost certainly taking a productivity hit as a whole.
Shortages due to shutdowns are a factor, but all the same, if there's a shortage of everything and an excess of cash, what do you get? (...Inflation).