So pathetic. Despite the vast amount of documentation the FTC demands (which seems wildly overbroad), I can answer their question in pretty complete substance here - for free.
1) how social media and video streaming services collect, use, track, estimate, or derive personal and demographic information;
Everything is tracked, and they have a very good idea of your demographic information. They track all interactions on the platform in giant data lakes, including clickstream activity showing sequences of actions, they collect all browser features, ip addresses etc, they collect all referral information. If their code is used by other websites, they collect all the clickstream and profile data from those services. They use publicly available datasets, census tract information, and datasets the govt provides such as DMV databases and voter registration files to enrich the data. They may synthesis what are called "features" from this data.
This is used for social media updates, fraud control and ad targeting among other purposes.
2) How they determine which ads and other content are shown to consumers;
Based on a machine learning models which look at the qualify and performance of ad copy related to folks who have been a) targeted by advertiser by specific criteria they then b) develop and estimate of which other users would also be interested and their level of interest based on all data points they maintain in the user profile, scored along an economic axis and user engagement and satisfaction targets (ie, all ads vs no ads).
3) Whether they apply algorithms or data analytics to personal information;
Yes - they do on a huge scale, and AWS / Google and others are busy designing custom chips to help speed up this type of analysis.
4) How they measure, promote, and research user engagement; and
They make their platforms as addictive as possible, with notifications, stimiulations. A popular book for these companies might be "Hooked: How to Build Habit-Forming Products" if the FTC actually cared about being educated at all in this space.
5) How their practices affect children and teens.
Affect them significantly, children are much easier to "hook", be it with computer games, e-cigs, or social media or even sugar or lack of sleep. The effects of all of these are very negative. Parents can have a power impact on these items.
Does anyone think social media companies do not use personal information and monetization of that to provide their hyperscale "free" services?