ROI is now seen as the "gold standard" for measuring the performance of marketing programs. ROI has been used for decades to evaluate all kinds of investments, and it's widely accepted by financial professionals. Some marketers believe that calculating the ROI of marketing activities will enhance their credibility in the C-suite.
Marketing ROI is certainly an important metric, but like any tool, it must be used in the right way for the right job. There is no single "magic metric" that can fully capture the effectiveness of marketing. So, it's important for marketers (as well as CEO's and CFO's) to understand the limitations of ROI for measuring marketing performance. I'll talk about some of the limitations and complexities here, but there are many others.
The basic ROI formula is extremely simple:
ROI = Return / Investment
The basic formula for marketing ROI (MROI) is almost as simple:
MROI = (Return - Marketing Investment) / Marketing Investment
Unfortunately, however, this simple formula hides a number of complexities. For example, what does the term "Return" mean? Total gross revenues or incremental gross revenues? Total gross margin or incremental gross margin? Total contribution margin or incremental contribution margin? The best answer is incremental contribution margin, although incremental gross margin is also widely used.
But now I've introduced a new term - incremental contribution margin - that requires a definition. Contribution margin is easy to define. It's total revenues less variable costs. The incremental part of the term is more complex. Marketing ROI experts tell us that, ideally, a marketing ROI calculation will measure the incremental (new) returns produced by incremental (new) marketing investments. So, supposedly, we can use marketing ROI to calculate the return on investment of an expanded TV advertising program, or a new direct mail program, or a new social media program.
Or can we? How can we really know which marketing program actually produced the incremental (new) contribution dollars, especially when we are running several marketing programs simultaneously. This won't always be a huge issue. For example, if we run a direct mail campaign that incorporates a discount coupon, we can count the number of coupons that are actually redeemed. But even this may not provide a completely accurate answer. What if a new customer had already been predisposed to buy because of an earlier marketing program? Should the discount coupon campaign get all of the "credit" for the new contribution margin associated with this new customer?
I am not suggesting that calculating marketing ROI is the equivalent of putting on a blindfold and throwing darts at a target. There are, in fact, well-accepted methods for dealing with the kinds of issues I've just described. I am trying to make the point that most marketing ROI "models" are based on numerous assumptions and judgment calls about the definition and the "allocation" of both returns and costs. This does not mean that marketing ROI has no value. It does mean that MROI often appears to be more precise than it actually is.