As per google February update non https sites flaghing as non secure. Google has been set a dead line of 23rd July 2018 with new chorome 68 update, google chrome will flag non secure (i.e http:// ) website as insecure.
After 23rd July 2018 you can see if your website belong to non secure category visitor rate gradually decreasing the reason your website stop showing on search results hence you will stop getting visitors from search engine.
As pe the google stats.
1. Over 68% of Chrome traffic on both Android and Windows is now protected
2. Over 78% of Chrome traffic on both Chrome OS and Mac is now protected
3. 81 of the top 100 sites on the web use HTTPS by default
Benefit of upgrading your http to https (Secure)
1. Not to loose your current website ranking
2. Customer can rely on your website that is secure and safe to visit.
3. Better performance
4. HTTPS helps prevent intruders from tampering with the communications between your websites and your users.