[?BUG?] Is "_year" intented to do something?

Hello,

I’ve played the game a few hours and it seems the oil supply is broken.

“_year,0-(0.015*x)” <-- This creates a permanent minus (never changing) of 75% to oil supply. Oil supply has a start value of 50%!!
That’s the reason I never had oil supply…

Is this a game bug and am I able to fix this with another time changing effect?