The study, which is based on responses from 351 top marketing executives, found that spending on digital marketing broadly is expected to jump 11% in the next year while traditional advertising budgets are expected to contract 3.6%. Despite the increasing investment in social media, it’s still difficult for marketers to quantify their return on investment. Only 15% of marketers in the study said they can show the impact of social media on their businesses using quantitative approaches, while 40% of marketers can only demonstrate the impact qualitatively. Nearly half of marketers said they haven’t been able to demonstrate the impact of social media spending on their business at all. Justifying how ad dollars get spent is a constant concern for marketers, who face increased pressure to deliver on margins and show results. Marketing spending typically generates more than 8% of company revenue, according to the Duke study. Marketing budgets are expected to increase more than 5% this year. Get the full story at The Wall Street Journal blog