Here's how it works:
1) Content relevance & backlinks get you to page 1.
2) User behavior factors keep you on page 1 - you MUST optimize these or you will fall out of the first page in a matter of days.
The most important behavioral factors are two: CTR & Bounce Rate. Both can and are tracked by Google with 100% accuracy. In order to stay on page 1 and keep climbing higher towards the top 3/5, you need both factors to work together. If you are just optimizing one of them, you are screwed. So, CTR does matter, but isolating & only optimizing it will not work. Before I explain how the logic works, some brief definitions first, so we are all on the same page:
CTR - click through rate; how many clicks you receive to your website for every X search queries, measured in %.
Bounce Rate - how many visitors get back to the SERPS-s after clicking & landing on your site. It is VERY IMPORTANT to notice that this has NOTHING to do with a website's bounce rate. Google does NOT take into account the bounce rate of a website, simply because it cannot track it for every site (only those that have GA installed) and therefore, the results would be highly inaccurate. However, Google can and does track if people come back to the search results and this is a negative signal, because if people go back to the SERP-s, that means they didn't find the information they were looking for on the website they clicked first.
Google has statistical data about the average CTR of every website in the top 10 for every search query/keyword. As someone else mentioned above, as an example, if you are at #5 and are supposed to receive in average 10% of the clicks, but you receive 15% for a "significant" period of time (which differs across niches), you will get bumped higher. BUT, if your bounce rate is higher than the average, you will get bumped down again.
Why do you think page speed matters as a ranking factor? It doesn't matter at all when you are on pages 2 and below. It does matter however when you are on the first page. Why? Simple really. Slow websites have higher bounce rates, which in turn signals the algorithm to bump you down until you fix your bounce rate %. Page speed is an indirect factor for bounce rate. Increasing page speed will lower bounce rates, especially if it's significant (going from 3-4 secs to less than 1 second for example). Of course, there are more factors which directly relate to bounce rate except page speed, but that's a topic for another thread.
So, to answer the OP's question: Yes, CTR matters, but bounce rate is just as important. Take care of both if you wanna stay on the first page for long-term.
