When the Build America Bond program ended there were two schools of thought. One argued that BABs would become an orphan class, with prices in the secondary market suffering from illiquidity. Another group thought there would be some scarcity value to the product and they would appreciate in value.
The scarcity camp won, according to Mike Pietronico, chief executive officer at Miller Tabak Asset Management. Scarcity has kept demand for BABs high and played a role in pushing yields lower.