To calculate the overall star rating and percentage breakdown by star, we don’t use a simple average. Instead, our system considers things like how recent a review is and if the reviewer bought the item on Amazon. It also analyses reviews to verify trustworthiness.
I used these to protect two small documents I keep in a divider on my desk. They were never handled, but the lamination curled off them after a short time. I can't imagine what would have happened if they'd been actively used.