The following I write from CoW1.0 perspective, but the thought is relevant for CoW1.5 just as well:

In CoW1.0, research costs and durations have a very similar, almost equally steep progression. I remember I had suggested it that way before it was realized a year ago, but I now see that's not perfect - because it results in the following: In every game, there comes a moment when your rares production reaches a speed that makes it sufficient for researching and building new level 1 ICs (need for the latter usually even decreases at a certain point and often that is the moment I'm talking about). It varies a lot when this moment comes, but you have it somewhere in each game. From that moment on you don't worry about resource costs any more when taking your resource decisions. From then on, you fill your two research slots all the time without compromise and you're from then on only interested in the duration of a certain technology when deciding which one to research next. While before that moment, you're only interested in the resource costs of a certain technology.
Now wouldn't it be much better if both resource requirements and duration of the technologies were relevant for your research decisions at any time? Was a rhetorical question - yes it would. Cause that would make research decisions much more difficult and interesting. You'd have to have two aspects in mind (scarcity of resources and scarcity of resource slots) that are very difficult to compare. A good strategy game should contain such difficult, multi-dimensional decisions.

To realize that, I suggest two improvements - at least one of these should be done; ideally both:
* The second research slot should be closed until day 8.
* Progression of resource costs should be steeper than it is now (i.e. low level technologies should cost less resources than they do now and high level technologies more than they do now). This would match the progress your economy makes during the game better.

In my experience, the average market value of rares in an average game is pretty close to twice the value of other resources. Which would speak for perfect resource balancing (since they're twice as hard to produce). Game would become pretty boring if the overall amount of rares in the game was increased - that would reduce your need to choose (thanks @WascallywabbitCDN for the illustration).
Of course if you're too greedy to pay that price for rares or during the first days think for whatever reason you have to research like there's no tomorrow... then you'll run into a severe rares shortage. But that's not the fault of the balancing - is your own fault, then.
Note: My suggestion to keep the second research slot closed during the first days (text on it should of course inform about the day it will open) would help players not to run into the trap of researching too much during early game.

However there's one issue hidden in rares having the scarcity and thus the value they deserve: Prize to buy them with gold is the same as for the other resources. Should be twice as high, of course. That should be fixed (maybe by reducing gold prize for other resources and increasing it for rares), but for sure not the overall amount of rares be increased.



Exactly. Also because as time goes by, you'll have built more and more IC and infra in the rares provinces of (at least) your core.
My suggestion to make progression of research costs more steep would help to even that out. Currently rares income increases as days go by, while need for rares doesn't (there is a peak at the moment most players want to build new IC level 1s, but afterwards it goes down while income keeps increasing) - which isn't a good balance. Steeper research costs progression would help to keep the value of rares more constant throughout the game.