OP is talking about "share of the world's wealth," not a fixed pie. While the raw amount of wealth (the pie) in the world does grow, the important measurement is what percentage of that pie is captured by the rich. And the rich are capturing an increasing percentage of the growing pie. That's where the inequality lies.
In a world of two people, where today I have one piece of bread and you have two, then tomorrow I have two pieces of bread and you have 10, I am worse off.
> the important measurement is what percentage of that pie is captured by the rich
And this is where we fundamentally disagree. I think the important measurement is how much pie the average person has. I think the important measurement is how much pie the people with the least pie have.
> In a world of two people, where today I have one piece of bread and you have two, then tomorrow I have two pieces of bread and you have 10, I am worse off.
If you think you're worse off in a world where you have twice as much stuff, just because your neighbor got more than you, to me, that speaks more to a psychological problem.
I was lucky enough to grow up in a safe, happy, secure, abundant, middle-class environment in the 90's. Meanwhile, Bill Gates was accumulating billions of dollars, more than 10,000x what my parents made. Despite that, I was happy, I did not feel worse off than middle class kids from generations before me, and I would certainly not trade away 50% of the fortunate childhood I had just to see Bill Gates cut down to size.
In a world of two people, where today I have one piece of bread and you have two, then tomorrow I have two pieces of bread and you have 10, I am worse off.