One of the key quantitative metrics is ROI. The Harvard Business Review defines marketing return on investment as:
(Incremental financial value derived from a marketing investment minus the cost of that marketing investment)
The cost of that marketing investment
In this ROI definition, the marketer must not only know what marketing costs, it must be able to gauge the financial value gained as a result of making that investment--not so easy.
Often, a company has difficulty attributing a sales increase (financial value) that occurs because of a particular marketing investment (such as one specific promotional campaign). So many influences can affect marketing results, including competition, other marketing efforts, economic conditions, consumer buying behavior, retailer activities and more. In fact, marketing that used to produce a certain result may no longer induce that same result.
Online marketing can be measured in clicks, for example, but there are also quantitative metrics that can prove valuable to long-term financial success--such as the sentiment of social media comments (positive or negative?). This can be measured, but how does a marketer relate that to financial value? And what about ROI of investing in influencer marketing, meaning paying for popular YouTube or Twitter celebs to promote a brand or product.
B2B marketers have to be accountable too, able to measure social media and other marketing efforts. Nonprofits are thinking long-term, not just measuring immediate marketing results from fundraising programmes and other activities.