Mayors have very little to do with economic disparity among their citizens. They set limited tax policy, limited role in education (particularly higher education), have a limited impact on the economy, etc. etc. etc.
But, for better or worse, it is strange that the economy almost always does better under Democratic presidents. The stock market (18 times higher under Democrats), corporate profits (12% rise under Democrats, 4.5% decline under Republicans), CEO and workers wages (disposable income rises 6 times faster under Democrats), unemployment, GDP growth (7 times more growth), the deficit (250% less debt under Democrats)... all are improve when
Democrats are in the White House. One or two presidents can be a fluke or just timing. But when you look at 80-90 years of presidencies the trend is crazy.
I would not have predicted a significant disparity. Correlation v. causation? Is 80-90 years a significant sample? No idea. But the disparity is just huge.
City Government must have a huge influence upon this. Take Texas for instance. Dallas is listed as 7th in the most unequal but Arlington list listed as 6th most equal. If you break down the list as a State you find that the most unequal is 5 Republicans and 5 Democrats (Governors). Whereas the most equal is 8 Republicans and 2 Democrats (Governors). Now if you take a list of the most unequal States the list changes to show Republicans as the worst.
10. Connecticut Democrat
Top 20% annual household income: Greater than $138,034
Bottom 20% annual household income: Less than $26,599
Income inequality factor: 5.19
9. California Democrat
Top 20%: Greater than $124,936
Bottom 20%: Less than $23,980
Income inequality factor: 5.21
8. New Jersey Republican
Top 20%: Greater than $141,057
Bottom 20%: Less than $27,002
Income inequality factor: 5.22
7. (tie) New Mexico Republican
Top 20%: Greater than $90,478
Bottom 20%: Less than $16,927
Income inequality factor: 5.35
7. (tie) Alabama Republican
Top 20%: Greater than $88,967
Bottom 20%: Less than $16,625
Income inequality factor: 5.35
5. Mississippi Republican
Top 20%: Greater than $79,596
Bottom 20%: Less than $14,509
Income inequality factor: 5.49
4. Massachusetts Republican
Top 20%: Greater than $134,004
Bottom 20%: Less than $24,181
Income inequality factor: 5.54
3. New York Democrat
Top 20%: Greater than $120,906
Bottom 20%: Less than $21,159
Income inequality factor: 5.71
2. Louisiana Republican
Top 20%: Greater than $94,740
Bottom 20%: Less than $16,322
Income inequality factor: 5.8
1. District of Columbia Democrat
Top 20%: Greater than $151,132
Bottom 20%: Less than $20,151
Income inequality factor: 7.5
So again I have to say that the city itself must have influence upon this in a much larger fashion than thought. Cities from the same State are on both sides of the list.
Per your second point.
I think the largest increase was Ford? I thought I read that somewhere. The disparity is huge as you say and I can't really put my finger on why, but I am not educated enough to even speculate as to why. My point remains though. Stocks and CEO's do MUCH better under Democrats, the wealthy see even more coin and the inequality widens and the continued lies still fly. Again, educate me where I am wrong here. I have a very open mind.