A similar question was asked about a year ago, but I didn't quite get the
answer I needed. I have a statistical spreadsheet. What I'm trying to do is
show the percentage increase/decrease of incidents in comparison to the
previous year.

Eg: A1= 31(this years numbers)
B1=47(last years numbers)

in C1 I want to display either -#% or +#% (depending on if the numbers have
increased or decreased compared to the previous year)

Someone gave the formula =(A1/B1)/A1 but I don't think that's quite right.