To calm frightened investors pulling out of muni-bond funds, Vanguard, which manages $115 billion in municipal bonds, has been tweeting excerpts from a new research commentary titled, "California is Not Greece."

On Facebook, the company is  promoting live video webinar featuring the company‘s muni-bond  experts. 

In the research commentary, authors Daniel W. Wallick, Christopher W. Alwine, and Michael A. Griffin argue that predictions of a rash of  defaults among state and local government are hyperbolic.

“Tax collections have begun to improve, and the broad U.S. economy is showing signs of sustained, albeit slow, recovery,” they wrote.

The $2.8 trillion U.S. municipal bond market includes thousands of issuers, with an average credit quality of AA. Moody’s Investors Service alone has ratings on more than 18,000 different issues from state and local governments. No state has failed to make a bond payment in more than 75 years.

In the 40 years ended 2009, 54 Moody’s-rated municipal bonds defaulted and the average five-year cumulative default rate for investment-grade municipal bonds was 0.03%, 1/30th that of corporate bonds.

Recently, despite dire warnings of imminent government collapse, since the middle of 2009, only three municipal issues in the “safe” sectors - general obligation, tax backed and essential services - have defaulted, according to Municipal Market Advisor’s data.

Retail investors own an estimated 70% of municipal debt, while mutual funds own about 17%. Many are wealthy investors who are typically more savvy than the average mutual fund investor, and don’t want to lock in losses by selling on bad headlines.