What is the relationship in growth between mainframe transaction processing and engagement applications?

Top of mind, as engagement applications continue to grow (ecommerce (also driven by social)), I suspect mainframe transaction processing will only continue to sustain its relevance. 

Need to research: how compute is allocated between mainframe and cloud. 

Analysis to conduct: observe rate of growth in top mainframe users (financials, retails) and analyze versus increased growth in online applications (see Citi report); note that 96 of top 100 banks still use main frame. 9 out of 10 largest insurance companies still run mainframe