Web trackers, on average, make some of the most-trafficked websites load twice as slow compared to when trackers are blocked, according to a new study published by Ghostery, a web tracker extension, and its parent company Cliqz.

Why it matters: A privacy reckoning around data collection from social media platforms has Americans paying more attention to how web trackers collect data, but this study shows that trackers aren't just a privacy problem. They can also cause terrible user experiences.

• According the 2018 Tracker Tax Report study — which looks at the top 500 websites in the United States as determined by Alexa — each tracker dropped onto a webpage costs a user a half-second in load times.
• The problem is pervasive. Nearly 90% of page loads had at least one tracker, according to the study. 65% had at least 10 trackers and about 20% had 50 or more trackers. Only 10% were tracker-free.
• Ghostery warns that "piggybacking," or trackers that give other trackers access to a website, can be problematic, as they often aid in the slowdown of websites and make it difficult for website owners to track which user data is being collected by third parties.

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