It depends on what niche you're in, how long the viewers are watching your videos, whether your videos are 5 minutes or longer (10 minutes or longer is even better, as it's great for optimization AND more ads, plus longer ads too), whether your viewers click other videos of yours or playlists and how long they stay on the channel, the location of the viewers, how big your channel is, how much the ad rates are being bought/sold for by certain advertisers, the time of the season/year, whether it's a mobile/desktop/etc. user, whether the user clicked an ad or watched it fully, and there's a bunch more determining factors. As you can see, pretty complex. That's why you have people earning as little as 1 cent per 1K views, or as much as $10.
Ad rates are falling due to more and more ads popping up and the fact that there's more channels to advertise on. Every year it'll continue a slow and steady drop unless something changes. It's nothing drastic, but that's why you don't have guaranteed CPM's anymore and such. My personal channel is making around 30 cents per every 1,000 views. It's that low because I also have some videos demonetized and not all my videos are exactly advertiser friendly.
