How big are the districts?

A few notes about the size of the districts. 

The number of jobs in each district:

6 Slums, Tracks

9 Midtown

10 Meatpack

11 Downtown, Westside

15 Russia

17 Italy, Hong Kong, France, Mexico

The approximate amount of energy needed to complete one trip through each district:

Slums 488

Tracks 1,410

Midtown 4,030

Meatpack 6,111

Downtown 5,581

Westside 7,376

Italy 9,858

Russia 13,041

Hong Kong 19,623

France TBD

Mexico TBD

The XP/Energy payoffs decline from 1.32 in Slums to 1.15 in Downtown. The next three are between 1.07 and 1.10, until you reach Hong Kong, where it plummets to 0.78. Yes, you put in more energy than you get back in XP. 

For some reason, it seems like it takes a month to 5* Italy (for an LSI build, longer for BSI), and only a couple of weeks for the next three. I think that's because by that time, an LSI is climbing up above 1500 Energy, and a refill or level-up gets you two stars. When I was at the end of Italy, it seemed like a level would only get me 1 star of progress. 

This game is more fun if you are patient. Set your expectations realistically. Then enjoy the journey, instead of dashing to the destination.