Audit fees have several advantages in measuring audit quality. One is that they are continuous and thus capture subtle
variations in quality. Another is that the literature has developed relatively sophisticated fee models with R-squares often
exceeding 70%, which to some extent alleviates concerns about correlated omitted variables.41 Audit fees also have
drawbacks that limit the interpretability of their results. One is that in addition to capturing audit effort, fees also capture
risk premia and improved audit efficiency (discussed in Section 4). This is a critical limitation because it means that an
increase in audit fees cannot be unambiguously interpreted as an increase in audit quality. A further limitation is that fees
capture the joint outcome of both supply and demand factors. Thus, researchers must take particular care in interpreting the
results from fee studies.