I see what yall @papa_meester and @Eddi_Bets are saying. BUT Players should know, when you STOP Building/Evolving your HMP WILL END! Also your City Ranking will Drop Drastically! 
And maybe y’all missed a word in that TIP? Facts are Facts! No opinions here! Your City will become “Static”.
Personally, I have a Constant Building Program that NEVER Ends! 
There is NO WAY or Reason in my mind I should let this happen? Thats just me. I have my “Recipe”! 
We ALL get to have FUN!!! making ours. 
On City Rankings… These show the “Production” of YOUR City. If your Production Drops, Your Rank WILL Follow.
Personally I use the City Rankings as a “Tool” to Measure MY City Building “Recipe” against the Recipes of my Fellow Players. 
Is my Thesis (8L3s Pay > 1L4) correct or not? That is an entire new topic.
It is just more of MY FUN!!! here.
Also @Eddi_Bets I am sure you know but Players do not have to participate, they can turn it Off. Just so they know.
And @papa_meester your interpetation of Tiers is confusing me? From what I see on my screen.
Legend Tiers…
Citys are Ranked by #
Tier 1 = #1 to #64
Tier 2 = #65 to #128
Tier 3 = #129 to #192
Tier 4 = #193 to #256
Looks like about 64 slots per Tier?
Getting up there is quite an acomplishment 
I appluad you! But as you are seeing, Staying is a little more difficult, Right? 