"MPA – The Association of Magazine Media is the primary advocate and voice for the magazine media industry, driving thought leadership and game‐changing strategies to promote the industry’s vitality, increase its revenues and grow market share."
Lots of good info - look under Research * Resources
"If someone were to tell you that the answers to your most pressing questions about building digital magazines, were already available, would you take the time to read them?
The information in the 2018 Mequoda Magazine Consumer Study will put you on a path to creating a multiplatform magazine that enlightens your readers and helps your publishing company grow and profit."
very brief synopsis at https://www.marketingcharts.com/cross-media-and-traditional/magazines-traditional-and-cross-channel-83731