The U.S. Postal Service expects employment to decrease due to the growing efficiency of mail processing and delivery through automation. Additionally, competition for jobs in the Postal Service is strong and comparatively few postal employees leave their jobs for other occupations before normal retirement age. Adding to challenges for employment growth are financial problems the Postal Service has encountered over the years, and occasional Congressional discussions about making the USPS a private enterprise. Discussions range from breaking up the four classes of mail to selling the entire enterprise to a private firm. However, the public's resistance to private postal service has restricted any major change in the Post Office.