Up arrow for increase, Down arrow for decrease, what for no change?

We have a web application that lists prices of a stocks and we have a requirement to indicate a movement. When there's an increase in price we add an up arrow, where there's a decrease in price we add a down arrow.

My thoughts are that we don't show anything as it's not moving, but I would like to validate this. The options that I see are:

• a thin dash (e.g. -),
• a thick dash (e.g.━),
• a (no change) label following the value
• nothing at all

What is the standard for indicating a values movement?