The gradual demise of U.S. agriculture is inevitable as the country climbs an "economic food chain," according to an agricultural economist at UC Davis. Steven C. Blank makes his case in his newly released book "The End of Agriculture in the American Portfolio." He says agricultural producers, who face both rising costs as well as price competition from imported commodities, are being forced out of economic necessity to find investments with better returns. "At some point, agriculture must be dropped entirely from the national portfolio because it cannot compete with the profitability of newer industries," says the author, who was raised on a cattle ranch in California. Blank says the United States is working its way up what he considers to be five progressively more lucrative levels of an "economic food chain." He says only about 1.5 percent of the population is still in the chain's first level: agriculture. The country is moving, he says, through resource-dependent industries to basic and high-tech manufacturing and, finally, to information production, which exploits capital and management. According to Blank, the progression is evident in two labor shortages: farmers are having difficulty finding laborers for low-paying physical work while the high-growth computer industry is using big salaries and creative recruitment methods in the competition for highly skilled workers. He says American food processors will continue to benefit from the economic changes that are creating an increased demand for ready-to-eat products. The range of available food products will continue to expand, he adds, and the cost of food relative to other products in America will remain almost constant.