The only way to figure it out would be to plug some entirely random values into the formulas, but the ideal city has an ER of 1.5, which is directly between the "1 and 2" that the rules refer to.
In the facility income rules you will find that your income is dependent on the Planetary Income Modifier or PIM in short. This PIM value is the only thing that is influenced by the employment rate (ER). The PIM is a function of ER, CR and TL.
If you take the CR and TL to be constants, you can solve the equation to figure out for what value of ER your PIM is maximal. This is the 1.5 value that Mikel mentioned.
If you take the TL to be constant, you can make a 3D graph to give you the dependence of the PIM on the ER and CR. This shows you how the PIM is more sensitive to CR than to ER. (in CR direction its linear, in ER direction its parabolic)
There are no datacards for facilities, but certain facilities are restricted to construction by certain faction types. Read the Rules for further details.
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"May the Grace of Ara go with you, and His Vengeance be wrought upon your enemies."
i read the rules and get confused, i'm retarded i know, but whenever i read the rules new questions pop up into my head -___-, so i usually prefer convos best way to understand for me.
so do i need data cards to build offices, hotels, taverns, high rises, power generators?
the only facilities that need data cards are the facilities that factions own aren't they ? (HQ's and stuff)
Perhaps not intuitively, the list of facilities that anyone can build are listed on the page for Faction Creation. Also listed on that page are the types of faction that can build any other specific facility.
All of the facilities you asked about are on the list of those available to all.
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"May the Grace of Ara go with you, and His Vengeance be wrought upon your enemies."