Should I use the simple past or the present perfect in the sentence below?
Over the past year, our company's sales increased/have increased by 85%.
Yes and then again it is surely less assertive. I think we can agree on that, can't we?
To agree with you would be to deny the reality that is English, Fil. Using have + past participle is actually a way for English speakers to be more assertive, more emphatic, more in your face, more of these same types of situations.
I have had enough of you! Get out. [just an example]
She has won the lottery!
I've got/gotten a miserable cold.