Are you in need of 14 case studies to back up the assertion that:
Moving subdomain -> subfolder (almost always) increases search traffic
Moving subfolder -> subdomain (almost always) decreases search traffic
I got your back. Thread /1

1) http://www.bloggingflail.com/subdomains-vs-subdirectories-seo/
2) https://iwantmyname.com/blog/2015/01/seo-penalties-of-moving-our-blog-to-a-subdomain
3) https://inbound.org/blog/the-sub-domain-vs-sub-directory-seo-debate-explained-in-one-flow-chart#comment-193514
4) https://twitter.com/dohertyjf/status/563868669864734721
5) https://growthhackers.com/articles/subdomain-vs-subdirectory-for-seo-a-2017-case-study
6) https://inbound.org/discuss/it-s-2014-what-s-the-latest-thinking-on-sub-domains-vs-sub-directories
/2

7) https://twitter.com/ruthburr/status/746119726946914304
8) http://www.bloggingflail.com/subdomains-vs-subdirectories-seo/
9) https://www.linkedin.com/pulse/case-study-how-single-change-boosted-organic-traffic-40-jesse-heap/
10) https://www.sistrix.com/blog/case-study-monsters-monster-growth-on-google/
11) https://www.sistrix.com/blog/subdomains-vs-subdirectories/
12) https://www.pi-datametrics.com/identify-seo-sub-domain-conflict-cannibalisation/
13) https://www.branded3.com/blog/choose-subdomain-subfolder-cctld-international/
14)
/3

Update - the folks from Marketing Sherpa wrote a piece on this topic, sharing some more examples and analysis: https://sherpablog.marketingsherpa.com/search-marketing/subfolders-subdirectories-subdomains-url-difference-increase-organic-traffic/