Google Advertising Network In A Nutshell
Google assesses as main metrics the change in its pay per clicks change and the change in its cost per click (defined as average amount Google charges advertisers for each engagement by users ).
An increase in paid clicks is a good sign of Google ability to attract advertisers on its platform. However, it needs to be assessed against Google cost per click change. More advertisers might spend less per clicks thus make the average revenues for Google decrease.
As you can see in 2017, the pay per clicks increased compared to 2016. However, it was offset by a decrease in cost per click. Google doesn’t show absolute numbers as this is kept secret.