Junk bonds, also known as high-yield bonds, are nothing more than speculative-grade (low-rated or unrated) bonds. Before 1977, almost all junk bonds were "fallen angels, " that is, bonds issued by firms that originally had investment-grade ratings but that had since been downgraded. In 1977, however, firms began to issue "original-issue junk."
Much of the credit for this innovation is given to Drexel Burnham Lambert, and especially its trader Michael Milken. Drexel had long enjoyed a niche as a junk bond trader and had established a network of potential investors in junk bonds. Its reasoning for marketing original-issue junk, so-called emerging credits, lay in the belief that default rates on these bonds did not justify the large yield spreads commonly exhibited in the marketplace. Firms not able to muster an investment-grade rating were happy to have Drexel (and other investment bankers) market their bonds directly to the public, as this opened up a new source of financing. Junk issues were a lower-cost financing alternative than borrowing from banks.