Andrew Willshire tweeted:
“ROI is often used as the metric of choice as though you should seek to maximise it, whereas that would result in under-investment and misallocation of budget. Much better to optimise on incremental revenue, but that’s often overlooked.”
I replied “Yup, that’s the essence of efficiency vs effectiveness” and quoted How Not to Plan: 66 Ways to Screw Up by Les Binet and Sarah Carter: “As you spend more on advertising, it often gets more effective (sales and profits generated go up), but less efficient (ROI goes down)… ROI…is a measure of efficiency, not effectiveness.”
Articles of Interest 