[Suicide Junkie]

Yes, so after 2 years, a CI-3 plant will get you only 6%.

Assuming your planet got knocked down to 0%, and IIRC, the planet modifiers are every 20% or so, it'll take 3 more years to get to harsh conditions.

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However, CI facilities, (and value improvement plants, too) will fully stack.
If you build two or three on the planet, you'll get the improvements 2 or 3 times faster.