Marketing is more than just colourful images, bows and curtains. It has a more valuable role to play when its insights are used to set the pace for the business.
What do you need to calculate the ROI of your marketing efforts? It’s not rocket science, but it requires similar diligence to track all of your spending by campaign.
Marketing activities can bring measurable ROI. At least for all external costs you should measure if it was worthwhile.