A line chart showing the percentage of the Bloomberg Municipal Bond Index rated AAA and the insurance penetration rate from 2002 through 2022. The AAA-rated portion of the Bloomberg Municipal Bond Index starts at around 60% in 2002, rises to around 70% by 2007, and then drops dramatically to roughly 15% by 2010 before holding stable through 2022. The insurance penetration rate follows a similar path, with the only difference being that it starts at around 50% from 2002 through 2007 before dropping to about 5% by 2010, where it remained into 2022.