While I agree that a symbol could be used to indicate the 3 states, I would also recommend using colour - perhaps red for price drop, green for price rise, black for no change. I wouldn't only use colour, primarily because of red-green colour blindness, but for a majority of people it would be a quicker visual cue to get an overview than using symbols.

While I agree that a symbol could be used to indicate each of the 3 states, I would also recommend using colour - perhaps red for price drop, green for price rise, black for no change. I wouldn't only use colour, primarily because of red-green colour blindness, but for a majority of people it would be a quicker visual cue to get an overview than using symbols.