 The drop in interest rates caused CD investors to pull their money back out of CDs and start looking for new high-yield instruments.It is not really clear how these former CD investors and the institutional property buyers found each other, but it seems that some petroleum-industry corporations based in Houston, Texas, ailing from the oil crisis, yet wanting to take advantage of low real estate prices for the expansion of gas station networks, could no longer qualify as easily for bank financing as they could in the early part of the decade.Wealthy CD investors in the same area, no longer able to achieve high yields from banks, may have found a solution to both their needs and those of their oil-industry counterparts by inventing the clap note.