You really need to explain why raising taxes doesn't raise revenue, because right now you're implying that no matter how much money is taken from people, the government will end up with the same amount, which is completely bonkers.
EDIT: It's as if Jimmy had 100 apples and the government is currently taking 10. But if the government decided to take 20 instead, the extra 10 would fall into a dimensional vortex and the government still ended up with 10. Taking 30 apples? 20 to the void. 50? The void takes 40. All of Jimmy's apples? Well then the vortex gets greedy and eats 90 apples, and that's a lot of apples.
Having apples is wealth. If you have a million apples, you give none of them to the government.
Picking apples is income.
That is taxed. Picking them takes time and effort, and the tax rate is graduated; so if you pick 30 apples you keep them all, and if you pick 100 apples then you give 50 to the government. More and more people decide they're happy with 30 apples instead of picking 70 more to get only 20 more for their own purposes, and the government gets the same amount of apples because that proportion of apple-pickers scaled back on their ambitions.
You need all tax sources if you are doing total income for GDP.
No. Not necessary. The capital gains tax also varies and also... has no effect on total revenues! You could argue that they're always--over the course of 80 frigging years of data--without fail in various administrations with various ideologies prompting the changes,
always adjusted in opposite directions. But that's actually not how it usually plays out. The fact is, revenue stays in a predictable band from 18% to 20% of GDP in many different administrations with many different policies.
There's a certain amount of total apples being picked that people on average are willing to give up to the government, and that's where is stays.