@jmjm -- This stuff requires a deeper understanding of how the tax code (in the USA) has changed from WW2 to present. Who (what classes of people) is being taxed and how it is collected/enforced, and the loopholes and who (or what class you have to be) to be able to take advantage of them.
One example to incorporate all of this...
Before banking and tight electronic record keeping, the government could only watch and enforce against the corporations. Over time, this shifted to workers.