In How Top Brands Are Using Facebook, Twitter and Instagram, Forrester Research outlined how more than 80% of top global brands actively post on Twitter, Facebook, Google+, LinkedIn and Instagram.
And they are doing so more often than before, with an average of 6.5 posts per brand per week on Facebook, up from 6.3 in 2014. Equivalent figures for Twitter were 18.3, up from 17.5, and for Instagram 4.9 times a week, up from 3.1.
Google+ was up marginally, from 3.5 posts a week to 3.6, Pinterest was unchanged on 9.9 while LinkedIn had dropped from 5.7 to 4.7.
But, Mobile Marketer reported, only Facebook had seen any growth in interaction by brands' social followers, up from 0.07% in 2014 to 0.22% this year, and that was in large part due to more brands paying to promote their Facebook posts to a larger number of users.
Instagram had by far the highest engagement rate, at 2.3%, but this had fallen sharply from 4.2% last year.
Similar proportional declines were evident elsewhere: the interaction rate on Pinterest dropped from 0.1% to 0.04%, on Google+ from 0.07% to 0.04%.
Twitter's already slight interaction rate slipped further, from 0.035% to 0.027%, while that on LinkedIn remained at around 0.05%.
"While B2C marketers are becoming more active on social networks, the vast majority of their followers haven't seemed to notice," said Nate Elliott, vp/principal analyst at Forrester Research and co-author of the report.
"Marketers are doing more work but generating less attention," he concluded.
Commenting on the findings in Forbes, consultant Blake Morgan observed that "most brands are not trying to win with helpfulness and relevance but rather traditional advertising – slapped on to social media".
She suggested that the pressure to make quarterly returns meant that social networking sites were putting revenue demands ahead of the user experience.
Data sourced from Mobile Marketer, Forbes; additional content by Warc staff