Pimco Fed watcher Paul McCulley quotes some intriguing insight from his boss, bond guru Bill Gross, into how the housing market works …

“The Plankton Theory, like life itself, begins and ends in the ocean. Plankton, of course, are almost microscopic organisms that serve as food for higher life forms. Without plankton almost every fish and mammal in the sea could not survive, since most species depend upon other fish for their existence and plankton are the initial building blocks of the entire process. Logic would suggest, therefore, that in attempting to forecast the well being of the Great White Whale, Jaws, or even Jaws II, that one of the factors to consider would be the status and future outlook of the plankton. That, in one hundred words or less, is the Plankton Theory.

Now, what possible significance could this have for the investment world? Plenty. Take for example, the area of real estate, especially that of single family housing. We’re all familiar with the rapid escalation of home prices over the last 10 years. For most Americans, their homes have been the best and in many cases the only investment that they have made in their entire lives. Some have gone so far as to invest in several homes and have endured ‘negative carry’ on the cash flow in anticipation of leveraged capital gains a few years down the road. But where does it stop? Can housing continue to increase at twice the Consumer Price Index for the next 10 years?

One way to measure might be via the Plankton Theory. In the case of real estate, the plankton would be the first-time buyer (perhaps a young married couple) with a desire to own their own home but with very little capital to carry it off. When the time comes that they can’t pull it off – either through an inability to come up with a down payment, or to service the monthly mortgage – then the ‘plankton’ would disappear and the rapid escalation in housing prices would ease as well. For, unless the current homeowner has someone to sell his house to, he’ll be unable to afford the house with the view or that extra bedroom, and the process would continue into the echelons of Beverly Hills and Shaker Heights. In the end, the entire market would wither on the investment vine and home prices would stop increasing at the same rapid rate. So to gauge the health of the housing market, look first at the plankton. Without their presence and financial vitality, the market’s not going to repeat the experience of the past 10 years.”

Gross wrote that in August 1980.