But regarding artists, you're sort of making my point: there are certainly more artists around that address essentially the whole world, as opposed to just themselves or their local area. Playing an instrument hasn't gotten easier (even that is arguable), but mastering music (at a mediocre level, maybe) has gotten easier, and distributing music has gotten way easier (presumably eventually that should affect the revenue split between labels and artists). And yes, all those artists of today are in competition with the artists of the past.
So there's certainly less money for each individual artist today, and there is more music available to me today, and I still don't have more time available to listen to much more of it.
But you do have a point regarding population growth.
Generally we have to adjust much more for inflation, as official inflation numbers are mostly fraudulent.
I agree with you on the cost of producing and distributing music going down, and I think it's fair to say that the creative part is easier and cheaper as well.
But don't people have more time to listen to music today when it is accessible everywhere?
Not if you adjust for inflation.
Not if you adjust for population growth.
Not if you adjust for growth in artists and music avaiable.
So in the end the money that goes to artists is worth maybe 10% of what it was in 1973, while serving a customer base that is 58% larger, probably much larger than that considering everybody has access now. And this money has to be split among many more artists than before, including many artists who have been dead for decades.