Growth, Part I

In the late 60's, Paul Ehrlich's The Population Bomb caused quite a stir in the pop-science community, because up until that point, we hadn't really thought much about our overall population on this earth, and how that might bring global consequences. Maybe people in the 60's didn't have the same concept of the unity and smallness of this orb. Nowadays, Beijing is practically next door, and the idea that China has 1.4 billion people has little to do with competition or war, and more to do with how early spring will come next year in Steamboat.
In 1968 Ehrlich calculted the earth's carrying capacity to be 3.8 billion. We've "proved him wrong" in the sense that the massive famines and wars that he predicted have not yet come to pass, but recently on the Brian Laer show, Ehrlich reiterated that global stability requires that we reduce our population to 5, or 4, or 3 billion.
Population reduction??? Are you f'ing kidding?? The definition of an economic recession, the concept that has caused so much constipation in the US over the past half year, is when "growth is negative for two or more consecutive quarters." In other words, if we are not growing and expanding, we are in trouble. In the context of this national Ponzi Scheme, how could we function if the world halved in population? Is there a possibility to create a new economic model under which we can reduce our population, contract sales and consumption, and at the same time maintain our political and social systems and our quality of life?