Light on or off?

When working at the PC/Laptop... do you leave your light off or switch it on?

I hardly ever use the light switch, but I happened to switch it on last night and the work I did increased somewhat 30% from my daily average - wasn't just quanity.. quality aswell

So i ask; Do you leave your light off or switch it on?



edit: bloody thing, i went to attach a poll but misclicked.. now we can't have a poll.