PALO ALTO, CA: Video posts on Instagram almost doubled in 2015, but over the same period the app's follower growth slowed and interaction rates declined by almost 40%, according to a new analysis.

As reported by VentureBeat, social media research firm Quintly examined 10,000 Instagram profiles over all of 2015 and found the number of video posts almost doubled from 1.78 per day at the beginning of the year to 2.77.

The average profile also grew relatively fast at the start of 2015, with average growth of 21%, but this had slowed to 16% growth by the end of the year. Quintly said it expected this trend to continue with follower growth slowing further in 2016.

However, one of the most surprising findings in the study was the discovery that the interaction rate on Instagram dropped from 4.96 to 3.10 during the year.

"Most surprising for me was the distinct drop in the interaction rate," said Julian Gottke, communications manager at Quintly. "Last year we reported Instagram as the 'king of engagement' and now the amount of interactions has dropped significantly."

He attributed the development to timelines getting increasingly crowded because of the higher post frequency rates on the average profile. That means more posts do not always translate into more interactions.

Secondly, the methodology for calculating the interaction rate – all interactions divided by posts and followers – means the more followers each profile gets, the smaller the interaction rate will be.

Despite these findings, Gottke went on to emphasise that he expected Instagram to continue to be a "meaningful network for brands and their storytelling".

He told VentureBeat: "Through its visual characteristics, it urges brands to be more creative and thus publish more interesting and less obtrusive content. This makes Instagram pleasant to use for consumers and, from a brand's point of view, the interactions will most likely stay higher compared to Facebook."

The report coincided with an announcement from Instagram that it is overhauling its feed so that photos will be prioritised according to a user's interests and friends rather than in chronological order. This is because the average user misses 70% of what is in their feed.

"As Instagram has grown, it's become harder to keep up with all the photos and videos people share. This means you often don't see the posts you might care about the most," the company said.

"To improve your experience, your feed will soon be ordered to show the moments you will care about the most. The order of photos and videos in your feed will be based on the likelihood you'll be interested in the content, your relationship with the person posting and the timeliness of the post."

Data sourced from Instagram, Quintly, VentureBeat; additional content by Warc staff