So there is no single metric Google uses to understand authority of your website. It uses muliple avenues to help it understand if your site is worthy, on a page by page basis. Read more below..
Google’s fight against problematic content has drawn renewed attention to a common question: how does Google know what’s authoritative? The simple answer is that it has no single “authority” metric. Rather, Google looks at a variety of undisclosed metrics which may even vary from query to query. The original authority metric: PageRank When Google first began, it did have a single authority figure. That was called PageRank, which was all about looking at links to pages. Google counted how many links a page received to help derive a PageRank score for that page.