Colorado & Iowa top states with registered organ donors

According to Donate Life America, the five states with the highest percentage of people registering as organ donors through their motor vehicle’s departments are as follows:

1. Colorado (64%)
2. Iowa (64%)
3. Montana (62%)
4. Wyoming (59%)
5. Washington (56%)

See Anne R. Carey & Veronica Salazar, Highest organ donor registration, USA Today, Dec. 29, 2009, at 1A.

I wonder why these states have the highest percentages rather than California and the New England states?