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.
But it works, works, works... so I'm torn. *shrug. I have eyebrows that are practically non-existent, so even the slightest change in color is noticeable. But holy buckets does it ever burn. And yes - make sure to purchase a developer - not included. Any level 10 developer will work.