Probably has to do with the fact that people who are teachers in Michigan are either new, or teachers from schools that are shut down.
Citation please? I know several people with teaching degrees in Michigan who would be very strong teachers, and stay in the state waiting for a current teacher to retire or die. This is in spite of the crappy salaries that await them.
There are people who want to teach because they understand the importance and nobility of it. Unfortunately, because the systems are so bloated with bad teachers (when even mediocrity should be considered unacceptable), many of these would-be excellent educators can't find a job.
Actually you can. One sixth of the world population already counts from 1 to 10 in one hand.
This would be a lot more useful if the natural choice for counting to zero on one hand wasn't reserved for 10.
Australians all let us rejoice,
For we are young and free;
"This generation may be the one that will face Armageddon." -- Ronald Reagan, "People" magazine, December 26, 1985