Marketers are expected to nearly double their social media spending in the next five years even though most can’t show the impact of social on their business, according to the biannual CMO Survey by Duke University’s Fuqua School of Business, the American Marketing Association and Deloitte, reports Ad Age.

The Ad Age report, in part, added:

“The survey, based on online responses from 289 marketers, revealed that social media spend currently makes up about 10.6% of marketing budgets and that number is expected to jump to 20.9% in five years. In 2009, marketers allocated just 5.6% of their budgets to social.

“Despite the increase in spend, almost half (47.9%) of marketers surveyed said they haven’t been able to show the impact yet on their business. More than 40% said they have a good qualitative sense of impact, while 11.5% said they can prove the impact of social quantitatively.

“On a scale from one to seven, companies in the survey rated the effectiveness of social being linked to their overall marketing strategies, with the mean rating coming out to 4.2.”