Well, a big question…
To start with, you can only measure ROI of any marketing activity – when you have clearly defined your objectives. Often times, that does not happen. Or they are not clear enough, thus, not measurable.
I have found this great infographic by MDGadvertising which gives some great food for thought how Social Media ROI can be measured.
If you want to dig deeper in the realm of measuring Event ROI, I can recommend the work of Elling Hamso’s Event ROI Institute. His methodology is based on the notion that an event is successful when you do things differently after the event than before. Events have different stakeholders: The budget owner/organizer, their board, the visitors, exhibitors, sponsors etc. All of them may have different objectives, hence their ROI has to be measured in different ways.
Find more details in the White Paper below.