Is Law of Diminishing Marginal Returns Objective Existence——An Analysis from Panel Data of Chinese Listed Company

To judge if the law of diminishing marginal returns is objective existence,the paper establishes a econometric panel data model with the data of 1238 Chinese listed company in 38 industry during 1998 to 2006. The result indicate that the law of diminishing marginal returns partially exist in secondary industry,but not exist in primary industry and tertiary-industry.So the law of diminishing marginal returns is not a general law.Tertiaryindustry used human resource as the major input factor has diminishing marginal returns,it imply that if a company's production satisfy the law of diminishing marginal returns is correlated with the human resource.The more human resource used by production may lead to the higher productivity of classical manufacturing,increasing marginal returns and diminishing marginal cost.