Attribution 4.0 International (CC BY 4.0)
http://www.flickr.com/photos/sfjalar/2949654021/
“In 1988, there were about 65,000 first-year teachers; by 2008, this number had grown to over 200,000 In 1988, the most common teacher was a veteran with 15 years of teaching experience. By 2008, the most common teacher was not a gray-haired veteran; he or she was a beginner in the first year of teaching. By that year, a quarter of the teaching force had five years or less of experience.” Data shows that between 40-50 percent of teachers leave within the first five years of their careers. This article goes into details.
One author’s thoughts about why teachers quit and why they stay.
Innovate * Inspire * Lead Change 
What are your thoughts?