Looking for examples of statistical data that would articulate the growth of user interface design in various ways - for example, number of interface design professionals, software applications, etc.
I have not come across anyone documenting this but here are some links that might help you.
Evolution of Cell Phone Design:http://www.webdesignerdepot.com/2009/05/the-evolution-of-cell-phone-design-between-1983-2009/
20 Years of Photoshop:http://www.webdesignerdepot.com/2010/02/20-years-of-adobe-photoshop/
A History of GUI:http://arstechnica.com/old/content/2005/05/gui.ars/
This one's interesting, a lot can be found here.http://www.google.co.in/search?q=user+interface+history&hl=en&sa=X&tbo=p&rlz=1C1GGLS_en-USIN291&tbs=tl:1,tll:1920,tlh:1929&ei=EdaxS8usBs6zrAeqkvTiAw&oi=timeline_histogram_nav&ct=timeline-histogram&cd=1&ved=0CGkQyQEoAQ
Hope this helps.