In a year, much has changed on social media networks. Facebook spent much of 2017 revamping its Trending section to squelch fake news. Instagram fared much better — as the company continued to celebrate the success of Instagram Stories (and the decline of Snapchat).

As you're planning for 2018, dedicate time to analyze your own brand's social strategy and see the changes for yourself. While you're at it, keep in mind these 2017 social media marketing trends that show no sign of slowing down.

1. Organic reach continues to plummet for brands and publishers on Facebook

After analyzing 880 million Facebook posts, the average engagement rate for brands and publishers has dropped 20 percent in 2017. That impact is compounded because SocialFlow research found the overall reach per post from January through May of 2016 was 42 percent less than 2015. Yikes.

If that wasn't bad enough, Facebook did a test and moved all non-ad posts from Pages in the News Feed to Facebook's new Explore feed in six countries. As you would guess, Pages received four times less engagement and lost up to 75 percent of their reach.

Companies are having to spend more and more to reach their core audience on Facebook. Keep that in mind as you plan for 2018.

2. Images and videos, coupled with fewer words, continue to reign (except on Twitter).

While engagement with links and images suffered the most this year on Facebook, video engagement held strong. Videos on Facebook now have, on average, double the engagement rate of other content types.

To optimize interactions, post videos between 60 and 90 seconds — or broadcast 15-minute live videos.

As visual continues to dominate social, Facebook posts at or below 50 characters have the most engagement. But Twitter has challenged that trend. This year, Twitter expanded their character count from 140 to 280.

3. Raw, authentic video and content, like Instagram Stories, win.

Instagram Stories have been the runaway hit of 2017. Launched in August of 2016, Instagram Stories had more than 250 million daily active users as of August 2017. Those under the age of 25 spend more than 32 minutes per day on Instagram, on average, while those 25 and older spend more than 24 minutes daily.

In short, Stories has become the reason to use Instagram. That's why 50 percent of businesses have now created a story. Often, the unedited content that captures real-life outperforms the pristine photos uploaded to Instagram itself.

In 2018, budget more time to create Stories like these that are proven to perform. They're what your audience most wants! Plus, Instagram Stories will continue to become a bigger player in 2018.

4. Be transparent about paid promotions and brand sponsorships on social media.

While less fun than the other trends, this is a major lesson for brands this year and in 2018.

The Federal Trade Commission (FTC) sent out nearly 100 warning letters to celebrities, cracking down on their social media endorsement policy. The policy states that if there is a "material connection an endorser and an advertiser, that connection should be clearly and conspicuously disclosed."

Encourage those in your influencer marketing programs to follow FTC recommendations, which means including clear tags like #sponsored or #ad in the first three lines of copy while avoiding ambiguous tags like #sp or #thankyou altogether. Or use this intuitive Instagram feature, which adds a paid partnership tag to posts.