Medicare Part B enrollment after age 65

Excerpt from http://www.ssa.gov/pubs/10043.html

If you do not enroll in Medicare Part B during your initial enrollment period, you have another chance each year to sign up during a "general enrollment period" from January 1 through March 31. Your coverage begins the following July. However, your monthly premium increases 10 percent for each 12-month period you were eligible for, but did not enroll in, Medicare Part B.