Google will reduce their pay to AdSense publishers than what advertisers bid for their ads if they think that a click of the ads does not provide much business value to the advertisers. This means that if an AdWords advertiser bids $1 on an ad, you as an AdSense publisher will get less than that $1 for the ad.
This is Google's attempt to protect the advertisers while at the same time trying to protect the entire advertisement ecosystem.
Smart pricing generally affect low quality sites as they don't normally attract quality traffic which in turn doesn't give good conversion to the advertisers. This is normally true for sites on video, games or wallpaper sites. You have the option to either improve the quality of your site (and attract quality visitors), or change to a new niche altogether.
Search engine traffic is considered a high quality traffic. This is because a visitor who comes from a search engine specifically search for a keyword and and come to your website from the search result. Your site's content should then cater to their search intent and the contextual nature of Google AdSense will bring more value to advertisers from the advertisements.
This is different from social media traffic as they are not as targeted and doesn't bring much value to advertisers.
If you're running multiple sites, and one of them is causing you to be smart-priced, consider using separate AdSense account for the low quality site. This is because smart pricing affects your entire account, and not just site-specific.
If your site has a number of ad units placed all over your sites, you might want to reduce it a bit. This is to make sure there are less accidental clicks from your site's visitors which doesn't give good conversion rate for the advertisers.
If there's nothing you can do about your site, or you just don't want to, you can just opt for other advertising options such as AdThrive or Mediavine. You can also monetize your site using affiliate programs.
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