It is very straightforward.  Specifically, i) Create an OIS baseline model of the firm’s income statement from last year, ii) relax its assumption of a fixed forecast and iii) the results will demonstrate how much profit the firm forfeited by not sizing and allocating last year’s marketing expenditures for the best possible profit.

To illustrate the business case, a simple proof of concept OIS model was created for the previous year’s income statement of an iconic global gift company. The results were astonishing: the firm had left 50-150% of last year’s profit on the table.  See the article, The OB Really Works for the details.