some files must be corrupted here. i just tested a fresh install, and neither of these influences are in place. Are you running any mods?
I recommend testing a fresh install of the game.
I think that when your GDP is low (below mid point), the productivity will decrease (bring a negative impact) but when ur GDP is high, the productivity will increase.
Also, when ur unemployment is high, it will bring negative effect to GDP but when unemployment is low it will bring pos effect to GDP. In the pic above is shows that unemployment brings positive effect which means in that situation during that moment, the unemployment is low (shown in separate unemplymnt graph)