From Longman Business Dictionary
yardstickyard·stick /ˈjɑːdˌstɪkˈjɑːrd-/ noun [countableC] something that you use to compare another thing with, in order to judge how good or successful it isyardstick ofIs profit the only yardstick of success?
The annual percentage rate is the best yardstick to use when comparing the costs of the different forms of credit.