I think its farily large. Just check out good book stores. There are so many new books coming out on self improvement. But thererae many players, good individual writers, speakers, even corporates like dale carnegie . I think only the best survive.
Sometimes there is no clear line where the self improvement end and corporate education starts. More competition

Suggested Reading:

Creating the Perfect Lifestyle (Success, Achievement, Motivation, Inspirational Self Help & Personal Development - akin to Tony Robbins, Oprah Winfrey, Jim Rohn)Book Reviews:

"Creating the Perfect Lifestyle is the must have book of the century. Its helpful advice can set you on the pathway of living... Read More >