I find different numbers depending on the source I look at but roughly 40 million guns were sold in the US in 2020 & 2021 combined. Everyone needs ammo for their guns so figure 50 rounds per box times the number of guns sold. That would be the number of rounds if each purchaser only wanted one box. Then figure the folks that want more ammo plus the old shooters that want to stock up and purchase cases of ammo in multiple calibers. Then there are those of us that reload and buy whatever we can find at as reasonable a price as we can find for primers, powder, brass and bullets. Then figure keeping police departments stocked and military.
How many billions or rounds, primers, cases and bullets does this amount to? Huge numbers. How many new shooters? How many old shooters? There’s a huge demand. I suspect the demand will ease one day but when.