Recent research done by SEMrush that took data from over 600,000 keywords worldwide and the first 100 SERP positions for each of them, was used to discover the top SEO ranking factors according to SERPs.  The results were compiled in to a list of alleged ranking factors that might influence page positions and influence page position in order of significance, from most to least influential:

The results

Direct website visits
Time on site
Pages per session
Bounce rate
Total referring domains
Total backlinks
Total referring IPs
Total follow-IPs
Content length
Website security (HTTPS)
Total anchors
Keyword in anchor
Keyword in body
Keyword density
Keywrod in title
Keyword in meta
Video on page

Key takeaways

1. Direct traffic is the most influential ranking factors i.e. when someone types in the actual domain name and goes directly to a website is a good sign to Google that the site has high authority and value.

2. User behavior signals such as time on site, pages per session and bounce rate also influence website rankings, since they indicate website quality and relevance for users.

3. Backlink factors are extremely important for rankings. Except for the factors related to anchor texts, all the backlink factors share 5th place in the importance chart.

4. All backlink factors impact one another. So your positions are unlikely to change if you boost the values for one factor but ignore others.

5. Branded keywords will always return more relevant but less popular websites on the first position.

6. The majority of domains in the high-volume group have an HTTPS version. But in the low-volume keyword groups the adoption rate is not so high, so implementing HTTPS would be a strong advantage against your competition.

7. The on-page SEO factors such as the presence of keywords in title, meta description and body of the text proved to be significantly less influential than other factors, however the adoption rate is impressive — keyword usage is one of the most popular SEO techniques.

Source: Semrush.com