The 30-day-visible-supply is the total par value of all new issue municipal bonds coming to market in the next 30 days.
Applying "30-Day Visible Supply" to Securities Exams:
To gauge the health of the new issue municipal bond market, dealers and investors will want to know how much total new debt is coming on the market. The 30 day visible supply will tell investors the total amount of new bonds being offered in the next month. The 30 day visible supply is published in The Daily Bond Buyer. An increase in the visible supply is bearish for bond prices as more bonds are going to be offered to investors. A fall in the 30 day visible supply is bullish for bonds as there will be fewer bonds offered for sale.